diff --git a/moor/example/example.g.dart b/moor/example/example.g.dart
index 47da5f36..336d8d8b 100644
--- a/moor/example/example.g.dart
+++ b/moor/example/example.g.dart
@@ -7,7 +7,7 @@ part of 'example.dart';
 // **************************************************************************
 
 // ignore_for_file: unnecessary_brace_in_string_interps
-class Category extends DataClass {
+class Category extends DataClass implements Insertable<Category> {
   final int id;
   final String description;
   Category({this.id, this.description});
@@ -39,13 +39,13 @@ class Category extends DataClass {
   }
 
   @override
-  CategoriesCompanion createCompanion(bool nullToAbsent) {
+  T createCompanion<T extends UpdateCompanion<Category>>(bool nullToAbsent) {
     return CategoriesCompanion(
       id: id == null && nullToAbsent ? const Value.absent() : Value.use(id),
       description: description == null && nullToAbsent
           ? const Value.absent()
           : Value.use(description),
-    );
+    ) as T;
   }
 
   Category copyWith({int id, String description}) => Category(
@@ -69,7 +69,7 @@ class Category extends DataClass {
       (other is Category && other.id == id && other.description == description);
 }
 
-class CategoriesCompanion implements UpdateCompanion<Category> {
+class CategoriesCompanion extends UpdateCompanion<Category> {
   final Value<int> id;
   final Value<String> description;
   const CategoriesCompanion({
@@ -147,13 +147,13 @@ class $CategoriesTable extends Categories
   }
 
   @override
-  Map<String, Variable> entityToSql(Category d, {bool includeNulls = false}) {
+  Map<String, Variable> entityToSql(CategoriesCompanion d) {
     final map = <String, Variable>{};
-    if (d.id != null || includeNulls) {
-      map['id'] = Variable<int, IntType>(d.id);
+    if (d.id.present) {
+      map['id'] = Variable<int, IntType>(d.id.value);
     }
-    if (d.description != null || includeNulls) {
-      map['description'] = Variable<String, StringType>(d.description);
+    if (d.description.present) {
+      map['description'] = Variable<String, StringType>(d.description.value);
     }
     return map;
   }
@@ -164,7 +164,7 @@ class $CategoriesTable extends Categories
   }
 }
 
-class Recipe extends DataClass {
+class Recipe extends DataClass implements Insertable<Recipe> {
   final int id;
   final String title;
   final String instructions;
@@ -206,7 +206,7 @@ class Recipe extends DataClass {
   }
 
   @override
-  RecipesCompanion createCompanion(bool nullToAbsent) {
+  T createCompanion<T extends UpdateCompanion<Recipe>>(bool nullToAbsent) {
     return RecipesCompanion(
       id: id == null && nullToAbsent ? const Value.absent() : Value.use(id),
       title: title == null && nullToAbsent
@@ -218,7 +218,7 @@ class Recipe extends DataClass {
       category: category == null && nullToAbsent
           ? const Value.absent()
           : Value.use(category),
-    );
+    ) as T;
   }
 
   Recipe copyWith({int id, String title, String instructions, int category}) =>
@@ -254,7 +254,7 @@ class Recipe extends DataClass {
           other.category == category);
 }
 
-class RecipesCompanion implements UpdateCompanion<Recipe> {
+class RecipesCompanion extends UpdateCompanion<Recipe> {
   final Value<int> id;
   final Value<String> title;
   final Value<String> instructions;
@@ -369,19 +369,19 @@ class $RecipesTable extends Recipes with TableInfo<$RecipesTable, Recipe> {
   }
 
   @override
-  Map<String, Variable> entityToSql(Recipe d, {bool includeNulls = false}) {
+  Map<String, Variable> entityToSql(RecipesCompanion d) {
     final map = <String, Variable>{};
-    if (d.id != null || includeNulls) {
-      map['id'] = Variable<int, IntType>(d.id);
+    if (d.id.present) {
+      map['id'] = Variable<int, IntType>(d.id.value);
     }
-    if (d.title != null || includeNulls) {
-      map['title'] = Variable<String, StringType>(d.title);
+    if (d.title.present) {
+      map['title'] = Variable<String, StringType>(d.title.value);
     }
-    if (d.instructions != null || includeNulls) {
-      map['instructions'] = Variable<String, StringType>(d.instructions);
+    if (d.instructions.present) {
+      map['instructions'] = Variable<String, StringType>(d.instructions.value);
     }
-    if (d.category != null || includeNulls) {
-      map['category'] = Variable<int, IntType>(d.category);
+    if (d.category.present) {
+      map['category'] = Variable<int, IntType>(d.category.value);
     }
     return map;
   }
@@ -392,7 +392,7 @@ class $RecipesTable extends Recipes with TableInfo<$RecipesTable, Recipe> {
   }
 }
 
-class Ingredient extends DataClass {
+class Ingredient extends DataClass implements Insertable<Ingredient> {
   final int id;
   final String name;
   final int caloriesPer100g;
@@ -428,7 +428,7 @@ class Ingredient extends DataClass {
   }
 
   @override
-  IngredientsCompanion createCompanion(bool nullToAbsent) {
+  T createCompanion<T extends UpdateCompanion<Ingredient>>(bool nullToAbsent) {
     return IngredientsCompanion(
       id: id == null && nullToAbsent ? const Value.absent() : Value.use(id),
       name:
@@ -436,7 +436,7 @@ class Ingredient extends DataClass {
       caloriesPer100g: caloriesPer100g == null && nullToAbsent
           ? const Value.absent()
           : Value.use(caloriesPer100g),
-    );
+    ) as T;
   }
 
   Ingredient copyWith({int id, String name, int caloriesPer100g}) => Ingredient(
@@ -466,7 +466,7 @@ class Ingredient extends DataClass {
           other.caloriesPer100g == caloriesPer100g);
 }
 
-class IngredientsCompanion implements UpdateCompanion<Ingredient> {
+class IngredientsCompanion extends UpdateCompanion<Ingredient> {
   final Value<int> id;
   final Value<String> name;
   final Value<int> caloriesPer100g;
@@ -566,16 +566,16 @@ class $IngredientsTable extends Ingredients
   }
 
   @override
-  Map<String, Variable> entityToSql(Ingredient d, {bool includeNulls = false}) {
+  Map<String, Variable> entityToSql(IngredientsCompanion d) {
     final map = <String, Variable>{};
-    if (d.id != null || includeNulls) {
-      map['id'] = Variable<int, IntType>(d.id);
+    if (d.id.present) {
+      map['id'] = Variable<int, IntType>(d.id.value);
     }
-    if (d.name != null || includeNulls) {
-      map['name'] = Variable<String, StringType>(d.name);
+    if (d.name.present) {
+      map['name'] = Variable<String, StringType>(d.name.value);
     }
-    if (d.caloriesPer100g != null || includeNulls) {
-      map['calories'] = Variable<int, IntType>(d.caloriesPer100g);
+    if (d.caloriesPer100g.present) {
+      map['calories'] = Variable<int, IntType>(d.caloriesPer100g.value);
     }
     return map;
   }
@@ -586,7 +586,8 @@ class $IngredientsTable extends Ingredients
   }
 }
 
-class IngredientInRecipe extends DataClass {
+class IngredientInRecipe extends DataClass
+    implements Insertable<IngredientInRecipe> {
   final int recipe;
   final int ingredient;
   final int amountInGrams;
@@ -623,7 +624,8 @@ class IngredientInRecipe extends DataClass {
   }
 
   @override
-  IngredientInRecipesCompanion createCompanion(bool nullToAbsent) {
+  T createCompanion<T extends UpdateCompanion<IngredientInRecipe>>(
+      bool nullToAbsent) {
     return IngredientInRecipesCompanion(
       recipe: recipe == null && nullToAbsent
           ? const Value.absent()
@@ -634,7 +636,7 @@ class IngredientInRecipe extends DataClass {
       amountInGrams: amountInGrams == null && nullToAbsent
           ? const Value.absent()
           : Value.use(amountInGrams),
-    );
+    ) as T;
   }
 
   IngredientInRecipe copyWith(
@@ -667,8 +669,7 @@ class IngredientInRecipe extends DataClass {
           other.amountInGrams == amountInGrams);
 }
 
-class IngredientInRecipesCompanion
-    implements UpdateCompanion<IngredientInRecipe> {
+class IngredientInRecipesCompanion extends UpdateCompanion<IngredientInRecipe> {
   final Value<int> recipe;
   final Value<int> ingredient;
   final Value<int> amountInGrams;
@@ -773,17 +774,16 @@ class $IngredientInRecipesTable extends IngredientInRecipes
   }
 
   @override
-  Map<String, Variable> entityToSql(IngredientInRecipe d,
-      {bool includeNulls = false}) {
+  Map<String, Variable> entityToSql(IngredientInRecipesCompanion d) {
     final map = <String, Variable>{};
-    if (d.recipe != null || includeNulls) {
-      map['recipe'] = Variable<int, IntType>(d.recipe);
+    if (d.recipe.present) {
+      map['recipe'] = Variable<int, IntType>(d.recipe.value);
     }
-    if (d.ingredient != null || includeNulls) {
-      map['ingredient'] = Variable<int, IntType>(d.ingredient);
+    if (d.ingredient.present) {
+      map['ingredient'] = Variable<int, IntType>(d.ingredient.value);
     }
-    if (d.amountInGrams != null || includeNulls) {
-      map['amount'] = Variable<int, IntType>(d.amountInGrams);
+    if (d.amountInGrams.present) {
+      map['amount'] = Variable<int, IntType>(d.amountInGrams.value);
     }
     return map;
   }
diff --git a/moor/lib/src/runtime/data_class.dart b/moor/lib/src/runtime/data_class.dart
index 7f4c7976..884732e0 100644
--- a/moor/lib/src/runtime/data_class.dart
+++ b/moor/lib/src/runtime/data_class.dart
@@ -3,6 +3,14 @@ import 'dart:convert';
 import 'package:meta/meta.dart';
 import 'package:moor/moor.dart';
 
+/// Common interface for objects which can be inserted or updated into a
+/// database.
+@optionalTypeArgs
+abstract class Insertable<D extends DataClass> {
+  /// Used internally by moor.
+  T createCompanion<T extends UpdateCompanion<D>>(bool nullToAbsent);
+}
+
 /// A common supertype for all data classes generated by moor. Data classes are
 /// immutable structures that represent a single row in a database table.
 abstract class DataClass {
@@ -26,9 +34,6 @@ abstract class DataClass {
   static dynamic parseJson(String jsonString) {
     return json.decode(jsonString);
   }
-
-  /// Used internally by moor.
-  UpdateCompanion createCompanion(bool nullToAbsent);
 }
 
 /// An update companion for a [DataClass] which is used to write data into a
@@ -36,7 +41,9 @@ abstract class DataClass {
 ///
 /// See also:
 /// - https://github.com/simolus3/moor/issues/25
-abstract class UpdateCompanion<D extends DataClass> {
+abstract class UpdateCompanion<D extends DataClass> implements Insertable {
+  const UpdateCompanion();
+
   /// Used internally by moor.
   ///
   /// Returns true if the column at the position [index] has been explicitly
@@ -44,6 +51,11 @@ abstract class UpdateCompanion<D extends DataClass> {
   // todo this doesn't need to exist anymore, remove before release and adapt
   // moor_generator
   bool isValuePresent(int index);
+
+  @override
+  T createCompanion<T extends UpdateCompanion>(bool nullToAbsent) {
+    return this as T;
+  }
 }
 
 /// A wrapper around arbitrary data [T] to indicate presence or absence
diff --git a/moor/lib/src/runtime/statements/delete.dart b/moor/lib/src/runtime/statements/delete.dart
index 19e1e7ef..f37d67e5 100644
--- a/moor/lib/src/runtime/statements/delete.dart
+++ b/moor/lib/src/runtime/statements/delete.dart
@@ -17,7 +17,7 @@ class DeleteStatement<T extends Table, D extends DataClass> extends Query<T, D>
   }
 
   /// Deletes just this entity. May not be used together with [where].
-  Future<int> delete(D entity) {
+  Future<int> delete(Insertable<D> entity) {
     assert(
         whereExpr == null,
         'When deleting an entity, you may not use where(...)'
diff --git a/moor/lib/src/runtime/statements/insert.dart b/moor/lib/src/runtime/statements/insert.dart
index 793c26de..e8dbddda 100644
--- a/moor/lib/src/runtime/statements/insert.dart
+++ b/moor/lib/src/runtime/statements/insert.dart
@@ -26,7 +26,7 @@ class InsertStatement<D extends DataClass> {
   ///
   /// If the table contains an auto-increment column, the generated value will
   /// be returned.
-  Future<int> insert(D entity, {bool orReplace = false}) async {
+  Future<int> insert(Insertable<D> entity, {bool orReplace = false}) async {
     _validateIntegrity(entity);
     final ctx = _createContext(entity, orReplace);
 
@@ -45,7 +45,8 @@ class InsertStatement<D extends DataClass> {
   /// When a row with the same primary or unique key already exists in the
   /// database, the insert will fail. Use [orReplace] to replace rows that
   /// already exist.
-  Future<void> insertAll(List<D> rows, {bool orReplace = false}) async {
+  Future<void> insertAll(List<Insertable<D>> rows,
+      {bool orReplace = false}) async {
     final statements = <String, List<GenerationContext>>{};
 
     // Not every insert has the same sql, as fields which are set to null are
@@ -78,12 +79,12 @@ class InsertStatement<D extends DataClass> {
   ///
   /// However, if no such row exists, a new row will be written instead.
   @Deprecated('Use insert with orReplace: true instead')
-  Future<void> insertOrReplace(D entity) async {
+  Future<void> insertOrReplace(Insertable<D> entity) async {
     return await insert(entity, orReplace: true);
   }
 
-  GenerationContext _createContext(D entry, bool replace) {
-    final map = table.entityToSql(entry)
+  GenerationContext _createContext(Insertable<D> entry, bool replace) {
+    final map = table.entityToSql(entry.createCompanion(true))
       ..removeWhere((_, value) => value == null);
 
     final ctx = GenerationContext.fromDb(database);
@@ -111,13 +112,12 @@ class InsertStatement<D extends DataClass> {
     return ctx;
   }
 
-  void _validateIntegrity(D d) {
+  void _validateIntegrity(Insertable<D> d) {
     if (d == null) {
       throw InvalidDataException(
           'Cannot writee null row into ${table.$tableName}');
     }
 
-    // todo needs to use d as update companion here
-    table.validateIntegrity(null).throwIfInvalid(d);
+    table.validateIntegrity(d.createCompanion(true)).throwIfInvalid(d);
   }
 }
diff --git a/moor/lib/src/runtime/statements/query.dart b/moor/lib/src/runtime/statements/query.dart
index 0642d4b7..925633ff 100644
--- a/moor/lib/src/runtime/statements/query.dart
+++ b/moor/lib/src/runtime/statements/query.dart
@@ -120,7 +120,7 @@ mixin SingleTableQueryMixin<T extends Table, D extends DataClass>
 
   /// Applies a [where] statement so that the row with the same primary key as
   /// [d] will be matched.
-  void whereSamePrimaryKey(D d) {
+  void whereSamePrimaryKey(Insertable<D> d) {
     assert(
         table.$primaryKey != null && table.$primaryKey.isNotEmpty,
         'When using Query.whereSamePrimaryKey, which is also called from '
@@ -136,7 +136,7 @@ mixin SingleTableQueryMixin<T extends Table, D extends DataClass>
 
     final primaryKeys = table.$primaryKey.map((c) => c.$name);
 
-    final updatedFields = table.entityToSql(d, includeNulls: true);
+    final updatedFields = table.entityToSql(d.createCompanion(false));
     // Extract values of the primary key as they are needed for the where clause
     final primaryKeyValues = Map.fromEntries(updatedFields.entries
         .where((entry) => primaryKeys.contains(entry.key)));
diff --git a/moor/lib/src/runtime/statements/update.dart b/moor/lib/src/runtime/statements/update.dart
index ffebf671..b085e498 100644
--- a/moor/lib/src/runtime/statements/update.dart
+++ b/moor/lib/src/runtime/statements/update.dart
@@ -55,11 +55,11 @@ class UpdateStatement<T extends Table, D extends DataClass> extends Query<T, D>
   ///
   /// See also: [replace], which does not require [where] statements and
   /// supports setting fields back to null.
-  Future<int> write(D entity) async {
+  Future<int> write(Insertable<D> entity) async {
     // todo needs to use entity as update companion here
     table.validateIntegrity(null).throwIfInvalid(entity);
 
-    _updatedFields = table.entityToSql(entity)
+    _updatedFields = table.entityToSql(entity.createCompanion(true))
       ..remove((_, value) => value == null);
 
     if (_updatedFields.isEmpty) {
@@ -86,13 +86,11 @@ class UpdateStatement<T extends Table, D extends DataClass> extends Query<T, D>
   ///    null values in the entity.
   ///  - [InsertStatement.insert] with the `orReplace` parameter, which behaves
   ///  similar to this method but creates a new row if none exists.
-  Future<bool> replace(D entity) async {
-    // We set isInserting to true here although we're in an update. This is
-    // because all the fields from the entity will be written (as opposed to a
-    // regular update, where only non-null fields will be written). If isInserted
-    // was false, the null fields would not be validated.
-    // todo needs to use entity as update companion here
-    table.validateIntegrity(null).throwIfInvalid(entity);
+  Future<bool> replace(Insertable<D> entity) async {
+    // We don't turn nulls to absent values here (as opposed to a regular
+    // update, where only non-null fields will be written).
+    final companion = entity.createCompanion(false);
+    table.validateIntegrity(companion).throwIfInvalid(entity);
     assert(
         whereExpr == null,
         'When using replace on an update statement, you may not use where(...)'
@@ -100,7 +98,7 @@ class UpdateStatement<T extends Table, D extends DataClass> extends Query<T, D>
 
     whereSamePrimaryKey(entity);
 
-    _updatedFields = table.entityToSql(entity, includeNulls: true);
+    _updatedFields = table.entityToSql(companion);
     final primaryKeys = table.$primaryKey.map((c) => c.$name);
 
     // Don't update the primary key
diff --git a/moor/lib/src/runtime/structure/table_info.dart b/moor/lib/src/runtime/structure/table_info.dart
index 6494c21f..c916ac32 100644
--- a/moor/lib/src/runtime/structure/table_info.dart
+++ b/moor/lib/src/runtime/structure/table_info.dart
@@ -38,15 +38,11 @@ mixin TableInfo<TableDsl extends Table, D extends DataClass> {
   /// that it respects all constraints (nullability, text length, etc.).
   VerificationContext validateIntegrity(covariant UpdateCompanion<D> instance);
 
-  /// Maps the given data class to a [Map] that can be inserted into sql. The
-  /// keys should represent the column name in sql, the values the corresponding
-  /// values of the field.
-  ///
-  /// If [includeNulls] is true, fields of the [D] that are null will be
-  /// written as a [Variable] with a value of null. Otherwise, these fields will
-  /// not be written into the map at all.
-  // todo migrate to update companions
-  Map<String, Variable> entityToSql(D instance, {bool includeNulls = false});
+  /// Maps the given update companion to a [Map] that can be inserted into sql.
+  /// The keys should represent the column name in sql, the values the
+  /// corresponding values of the field. All fields of the [instance] which are
+  /// present will be written, absent fields will be omitted.
+  Map<String, Variable> entityToSql(covariant UpdateCompanion<D> instance);
 
   /// Maps the given row returned by the database into the fitting data class.
   D map(Map<String, dynamic> data, {String tablePrefix});
diff --git a/moor/test/data/tables/todos.g.dart b/moor/test/data/tables/todos.g.dart
index 101601a1..de2368e1 100644
--- a/moor/test/data/tables/todos.g.dart
+++ b/moor/test/data/tables/todos.g.dart
@@ -7,7 +7,7 @@ part of 'todos.dart';
 // **************************************************************************
 
 // ignore_for_file: unnecessary_brace_in_string_interps
-class TodoEntry extends DataClass {
+class TodoEntry extends DataClass implements Insertable<TodoEntry> {
   final int id;
   final String title;
   final String content;
@@ -56,7 +56,7 @@ class TodoEntry extends DataClass {
   }
 
   @override
-  TodosTableCompanion createCompanion(bool nullToAbsent) {
+  T createCompanion<T extends UpdateCompanion<TodoEntry>>(bool nullToAbsent) {
     return TodosTableCompanion(
       id: id == null && nullToAbsent ? const Value.absent() : Value.use(id),
       title: title == null && nullToAbsent
@@ -71,7 +71,7 @@ class TodoEntry extends DataClass {
       category: category == null && nullToAbsent
           ? const Value.absent()
           : Value.use(category),
-    );
+    ) as T;
   }
 
   TodoEntry copyWith(
@@ -116,7 +116,7 @@ class TodoEntry extends DataClass {
           other.category == category);
 }
 
-class TodosTableCompanion implements UpdateCompanion<TodoEntry> {
+class TodosTableCompanion extends UpdateCompanion<TodoEntry> {
   final Value<int> id;
   final Value<String> title;
   final Value<String> content;
@@ -251,22 +251,22 @@ class $TodosTableTable extends TodosTable
   }
 
   @override
-  Map<String, Variable> entityToSql(TodoEntry d, {bool includeNulls = false}) {
+  Map<String, Variable> entityToSql(TodosTableCompanion d) {
     final map = <String, Variable>{};
-    if (d.id != null || includeNulls) {
-      map['id'] = Variable<int, IntType>(d.id);
+    if (d.id.present) {
+      map['id'] = Variable<int, IntType>(d.id.value);
     }
-    if (d.title != null || includeNulls) {
-      map['title'] = Variable<String, StringType>(d.title);
+    if (d.title.present) {
+      map['title'] = Variable<String, StringType>(d.title.value);
     }
-    if (d.content != null || includeNulls) {
-      map['content'] = Variable<String, StringType>(d.content);
+    if (d.content.present) {
+      map['content'] = Variable<String, StringType>(d.content.value);
     }
-    if (d.targetDate != null || includeNulls) {
-      map['target_date'] = Variable<DateTime, DateTimeType>(d.targetDate);
+    if (d.targetDate.present) {
+      map['target_date'] = Variable<DateTime, DateTimeType>(d.targetDate.value);
     }
-    if (d.category != null || includeNulls) {
-      map['category'] = Variable<int, IntType>(d.category);
+    if (d.category.present) {
+      map['category'] = Variable<int, IntType>(d.category.value);
     }
     return map;
   }
@@ -277,7 +277,7 @@ class $TodosTableTable extends TodosTable
   }
 }
 
-class Category extends DataClass {
+class Category extends DataClass implements Insertable<Category> {
   final int id;
   final String description;
   Category({this.id, this.description});
@@ -309,13 +309,13 @@ class Category extends DataClass {
   }
 
   @override
-  CategoriesCompanion createCompanion(bool nullToAbsent) {
+  T createCompanion<T extends UpdateCompanion<Category>>(bool nullToAbsent) {
     return CategoriesCompanion(
       id: id == null && nullToAbsent ? const Value.absent() : Value.use(id),
       description: description == null && nullToAbsent
           ? const Value.absent()
           : Value.use(description),
-    );
+    ) as T;
   }
 
   Category copyWith({int id, String description}) => Category(
@@ -339,7 +339,7 @@ class Category extends DataClass {
       (other is Category && other.id == id && other.description == description);
 }
 
-class CategoriesCompanion implements UpdateCompanion<Category> {
+class CategoriesCompanion extends UpdateCompanion<Category> {
   final Value<int> id;
   final Value<String> description;
   const CategoriesCompanion({
@@ -414,13 +414,13 @@ class $CategoriesTable extends Categories
   }
 
   @override
-  Map<String, Variable> entityToSql(Category d, {bool includeNulls = false}) {
+  Map<String, Variable> entityToSql(CategoriesCompanion d) {
     final map = <String, Variable>{};
-    if (d.id != null || includeNulls) {
-      map['id'] = Variable<int, IntType>(d.id);
+    if (d.id.present) {
+      map['id'] = Variable<int, IntType>(d.id.value);
     }
-    if (d.description != null || includeNulls) {
-      map['desc'] = Variable<String, StringType>(d.description);
+    if (d.description.present) {
+      map['desc'] = Variable<String, StringType>(d.description.value);
     }
     return map;
   }
@@ -431,7 +431,7 @@ class $CategoriesTable extends Categories
   }
 }
 
-class User extends DataClass {
+class User extends DataClass implements Insertable<User> {
   final int id;
   final String name;
   final bool isAwesome;
@@ -485,7 +485,7 @@ class User extends DataClass {
   }
 
   @override
-  UsersCompanion createCompanion(bool nullToAbsent) {
+  T createCompanion<T extends UpdateCompanion<User>>(bool nullToAbsent) {
     return UsersCompanion(
       id: id == null && nullToAbsent ? const Value.absent() : Value.use(id),
       name:
@@ -499,7 +499,7 @@ class User extends DataClass {
       creationTime: creationTime == null && nullToAbsent
           ? const Value.absent()
           : Value.use(creationTime),
-    );
+    ) as T;
   }
 
   User copyWith(
@@ -545,7 +545,7 @@ class User extends DataClass {
           other.creationTime == creationTime);
 }
 
-class UsersCompanion implements UpdateCompanion<User> {
+class UsersCompanion extends UpdateCompanion<User> {
   final Value<int> id;
   final Value<String> name;
   final Value<bool> isAwesome;
@@ -680,22 +680,24 @@ class $UsersTable extends Users with TableInfo<$UsersTable, User> {
   }
 
   @override
-  Map<String, Variable> entityToSql(User d, {bool includeNulls = false}) {
+  Map<String, Variable> entityToSql(UsersCompanion d) {
     final map = <String, Variable>{};
-    if (d.id != null || includeNulls) {
-      map['id'] = Variable<int, IntType>(d.id);
+    if (d.id.present) {
+      map['id'] = Variable<int, IntType>(d.id.value);
     }
-    if (d.name != null || includeNulls) {
-      map['name'] = Variable<String, StringType>(d.name);
+    if (d.name.present) {
+      map['name'] = Variable<String, StringType>(d.name.value);
     }
-    if (d.isAwesome != null || includeNulls) {
-      map['is_awesome'] = Variable<bool, BoolType>(d.isAwesome);
+    if (d.isAwesome.present) {
+      map['is_awesome'] = Variable<bool, BoolType>(d.isAwesome.value);
     }
-    if (d.profilePicture != null || includeNulls) {
-      map['profile_picture'] = Variable<Uint8List, BlobType>(d.profilePicture);
+    if (d.profilePicture.present) {
+      map['profile_picture'] =
+          Variable<Uint8List, BlobType>(d.profilePicture.value);
     }
-    if (d.creationTime != null || includeNulls) {
-      map['creation_time'] = Variable<DateTime, DateTimeType>(d.creationTime);
+    if (d.creationTime.present) {
+      map['creation_time'] =
+          Variable<DateTime, DateTimeType>(d.creationTime.value);
     }
     return map;
   }
@@ -706,7 +708,7 @@ class $UsersTable extends Users with TableInfo<$UsersTable, User> {
   }
 }
 
-class SharedTodo extends DataClass {
+class SharedTodo extends DataClass implements Insertable<SharedTodo> {
   final int todo;
   final int user;
   SharedTodo({this.todo, this.user});
@@ -736,13 +738,13 @@ class SharedTodo extends DataClass {
   }
 
   @override
-  SharedTodosCompanion createCompanion(bool nullToAbsent) {
+  T createCompanion<T extends UpdateCompanion<SharedTodo>>(bool nullToAbsent) {
     return SharedTodosCompanion(
       todo:
           todo == null && nullToAbsent ? const Value.absent() : Value.use(todo),
       user:
           user == null && nullToAbsent ? const Value.absent() : Value.use(user),
-    );
+    ) as T;
   }
 
   SharedTodo copyWith({int todo, int user}) => SharedTodo(
@@ -766,7 +768,7 @@ class SharedTodo extends DataClass {
       (other is SharedTodo && other.todo == todo && other.user == user);
 }
 
-class SharedTodosCompanion implements UpdateCompanion<SharedTodo> {
+class SharedTodosCompanion extends UpdateCompanion<SharedTodo> {
   final Value<int> todo;
   final Value<int> user;
   const SharedTodosCompanion({
@@ -847,13 +849,13 @@ class $SharedTodosTable extends SharedTodos
   }
 
   @override
-  Map<String, Variable> entityToSql(SharedTodo d, {bool includeNulls = false}) {
+  Map<String, Variable> entityToSql(SharedTodosCompanion d) {
     final map = <String, Variable>{};
-    if (d.todo != null || includeNulls) {
-      map['todo'] = Variable<int, IntType>(d.todo);
+    if (d.todo.present) {
+      map['todo'] = Variable<int, IntType>(d.todo.value);
     }
-    if (d.user != null || includeNulls) {
-      map['user'] = Variable<int, IntType>(d.user);
+    if (d.user.present) {
+      map['user'] = Variable<int, IntType>(d.user.value);
     }
     return map;
   }
@@ -864,7 +866,8 @@ class $SharedTodosTable extends SharedTodos
   }
 }
 
-class TableWithoutPKData extends DataClass {
+class TableWithoutPKData extends DataClass
+    implements Insertable<TableWithoutPKData> {
   final int notReallyAnId;
   final double someFloat;
   TableWithoutPKData({this.notReallyAnId, this.someFloat});
@@ -898,7 +901,8 @@ class TableWithoutPKData extends DataClass {
   }
 
   @override
-  TableWithoutPKCompanion createCompanion(bool nullToAbsent) {
+  T createCompanion<T extends UpdateCompanion<TableWithoutPKData>>(
+      bool nullToAbsent) {
     return TableWithoutPKCompanion(
       notReallyAnId: notReallyAnId == null && nullToAbsent
           ? const Value.absent()
@@ -906,7 +910,7 @@ class TableWithoutPKData extends DataClass {
       someFloat: someFloat == null && nullToAbsent
           ? const Value.absent()
           : Value.use(someFloat),
-    );
+    ) as T;
   }
 
   TableWithoutPKData copyWith({int notReallyAnId, double someFloat}) =>
@@ -934,7 +938,7 @@ class TableWithoutPKData extends DataClass {
           other.someFloat == someFloat);
 }
 
-class TableWithoutPKCompanion implements UpdateCompanion<TableWithoutPKData> {
+class TableWithoutPKCompanion extends UpdateCompanion<TableWithoutPKData> {
   final Value<int> notReallyAnId;
   final Value<double> someFloat;
   const TableWithoutPKCompanion({
@@ -1019,14 +1023,13 @@ class $TableWithoutPKTable extends TableWithoutPK
   }
 
   @override
-  Map<String, Variable> entityToSql(TableWithoutPKData d,
-      {bool includeNulls = false}) {
+  Map<String, Variable> entityToSql(TableWithoutPKCompanion d) {
     final map = <String, Variable>{};
-    if (d.notReallyAnId != null || includeNulls) {
-      map['not_really_an_id'] = Variable<int, IntType>(d.notReallyAnId);
+    if (d.notReallyAnId.present) {
+      map['not_really_an_id'] = Variable<int, IntType>(d.notReallyAnId.value);
     }
-    if (d.someFloat != null || includeNulls) {
-      map['some_float'] = Variable<double, RealType>(d.someFloat);
+    if (d.someFloat.present) {
+      map['some_float'] = Variable<double, RealType>(d.someFloat.value);
     }
     return map;
   }
diff --git a/moor_flutter/example/lib/database/database.g.dart b/moor_flutter/example/lib/database/database.g.dart
index 699185bb..94076fe4 100644
--- a/moor_flutter/example/lib/database/database.g.dart
+++ b/moor_flutter/example/lib/database/database.g.dart
@@ -7,7 +7,7 @@ part of 'database.dart';
 // **************************************************************************
 
 // ignore_for_file: unnecessary_brace_in_string_interps
-class TodoEntry extends DataClass {
+class TodoEntry extends DataClass implements Insertable<TodoEntry> {
   final int id;
   final String content;
   final DateTime targetDate;
@@ -49,6 +49,22 @@ class TodoEntry extends DataClass {
     };
   }
 
+  @override
+  T createCompanion<T extends UpdateCompanion<TodoEntry>>(bool nullToAbsent) {
+    return TodosCompanion(
+      id: id == null && nullToAbsent ? const Value.absent() : Value.use(id),
+      content: content == null && nullToAbsent
+          ? const Value.absent()
+          : Value.use(content),
+      targetDate: targetDate == null && nullToAbsent
+          ? const Value.absent()
+          : Value.use(targetDate),
+      category: category == null && nullToAbsent
+          ? const Value.absent()
+          : Value.use(category),
+    ) as T;
+  }
+
   TodoEntry copyWith(
           {int id, String content, DateTime targetDate, int category}) =>
       TodoEntry(
@@ -83,6 +99,35 @@ class TodoEntry extends DataClass {
           other.category == category);
 }
 
+class TodosCompanion extends UpdateCompanion<TodoEntry> {
+  final Value<int> id;
+  final Value<String> content;
+  final Value<DateTime> targetDate;
+  final Value<int> category;
+  const TodosCompanion({
+    this.id = const Value.absent(),
+    this.content = const Value.absent(),
+    this.targetDate = const Value.absent(),
+    this.category = const Value.absent(),
+  });
+  @override
+  bool isValuePresent(int index) {
+    switch (index) {
+      case 0:
+        return id.present;
+      case 1:
+        return content.present;
+      case 2:
+        return targetDate.present;
+      case 3:
+        return category.present;
+      default:
+        throw ArgumentError(
+            'Hit an invalid state while serializing data. Did you run the build step?');
+    }
+  }
+}
+
 class $TodosTable extends Todos with TableInfo<$TodosTable, TodoEntry> {
   final GeneratedDatabase _db;
   final String _alias;
@@ -138,22 +183,26 @@ class $TodosTable extends Todos with TableInfo<$TodosTable, TodoEntry> {
   @override
   final String actualTableName = 'todos';
   @override
-  VerificationContext validateIntegrity(TodoEntry instance, bool isInserting) =>
-      VerificationContext()
-        ..handle(
-            _idMeta, id.isAcceptableValue(instance.id, isInserting, _idMeta))
-        ..handle(
-            _contentMeta,
-            content.isAcceptableValue(
-                instance.content, isInserting, _contentMeta))
-        ..handle(
-            _targetDateMeta,
-            targetDate.isAcceptableValue(
-                instance.targetDate, isInserting, _targetDateMeta))
-        ..handle(
-            _categoryMeta,
-            category.isAcceptableValue(
-                instance.category, isInserting, _categoryMeta));
+  VerificationContext validateIntegrity(TodosCompanion d) {
+    final context = VerificationContext();
+    if (d.isValuePresent(0)) {
+      context.handle(_idMeta, id.isAcceptableValue(d.id.value, _idMeta));
+    }
+    if (d.isValuePresent(1)) {
+      context.handle(_contentMeta,
+          content.isAcceptableValue(d.content.value, _contentMeta));
+    }
+    if (d.isValuePresent(2)) {
+      context.handle(_targetDateMeta,
+          targetDate.isAcceptableValue(d.targetDate.value, _targetDateMeta));
+    }
+    if (d.isValuePresent(3)) {
+      context.handle(_categoryMeta,
+          category.isAcceptableValue(d.category.value, _categoryMeta));
+    }
+    return context;
+  }
+
   @override
   Set<GeneratedColumn> get $primaryKey => {id};
   @override
@@ -186,7 +235,7 @@ class $TodosTable extends Todos with TableInfo<$TodosTable, TodoEntry> {
   }
 }
 
-class Category extends DataClass {
+class Category extends DataClass implements Insertable<Category> {
   final int id;
   final String description;
   Category({this.id, this.description});
@@ -217,6 +266,16 @@ class Category extends DataClass {
     };
   }
 
+  @override
+  T createCompanion<T extends UpdateCompanion<Category>>(bool nullToAbsent) {
+    return CategoriesCompanion(
+      id: id == null && nullToAbsent ? const Value.absent() : Value.use(id),
+      description: description == null && nullToAbsent
+          ? const Value.absent()
+          : Value.use(description),
+    ) as T;
+  }
+
   Category copyWith({int id, String description}) => Category(
         id: id ?? this.id,
         description: description ?? this.description,
@@ -238,6 +297,27 @@ class Category extends DataClass {
       (other is Category && other.id == id && other.description == description);
 }
 
+class CategoriesCompanion extends UpdateCompanion<Category> {
+  final Value<int> id;
+  final Value<String> description;
+  const CategoriesCompanion({
+    this.id = const Value.absent(),
+    this.description = const Value.absent(),
+  });
+  @override
+  bool isValuePresent(int index) {
+    switch (index) {
+      case 0:
+        return id.present;
+      case 1:
+        return description.present;
+      default:
+        throw ArgumentError(
+            'Hit an invalid state while serializing data. Did you run the build step?');
+    }
+  }
+}
+
 class $CategoriesTable extends Categories
     with TableInfo<$CategoriesTable, Category> {
   final GeneratedDatabase _db;
@@ -274,14 +354,18 @@ class $CategoriesTable extends Categories
   @override
   final String actualTableName = 'categories';
   @override
-  VerificationContext validateIntegrity(Category instance, bool isInserting) =>
-      VerificationContext()
-        ..handle(
-            _idMeta, id.isAcceptableValue(instance.id, isInserting, _idMeta))
-        ..handle(
-            _descriptionMeta,
-            description.isAcceptableValue(
-                instance.description, isInserting, _descriptionMeta));
+  VerificationContext validateIntegrity(CategoriesCompanion d) {
+    final context = VerificationContext();
+    if (d.isValuePresent(0)) {
+      context.handle(_idMeta, id.isAcceptableValue(d.id.value, _idMeta));
+    }
+    if (d.isValuePresent(1)) {
+      context.handle(_descriptionMeta,
+          description.isAcceptableValue(d.description.value, _descriptionMeta));
+    }
+    return context;
+  }
+
   @override
   Set<GeneratedColumn> get $primaryKey => {id};
   @override
diff --git a/moor_generator/lib/src/writer/data_class_writer.dart b/moor_generator/lib/src/writer/data_class_writer.dart
index 05118312..c5a86dff 100644
--- a/moor_generator/lib/src/writer/data_class_writer.dart
+++ b/moor_generator/lib/src/writer/data_class_writer.dart
@@ -12,7 +12,8 @@ class DataClassWriter {
   DataClassWriter(this.table, this.options);
 
   void writeInto(StringBuffer buffer) {
-    buffer.write('class ${table.dartTypeName} extends DataClass {\n');
+    buffer.write(
+        'class ${table.dartTypeName} extends DataClass implements Insertable<${table.dartTypeName}> {\n');
 
     // write individual fields
     for (var column in table.columns) {
@@ -218,18 +219,19 @@ class DataClassWriter {
   }
 
   void _writeCompanionOverride(StringBuffer buffer) {
-    // UpdateCompanion<D> createCompanion(bool nullToAbsent);
+    // T createCompanion<T extends UpdateCompanion>(bool nullToAbsent)
+
     final companionClass = table.updateCompanionName;
-    buffer.write('@override\n$companionClass '
-        'createCompanion(bool nullToAbsent) {\n'
-        'return $companionClass(');
+    buffer.write('@override\nT createCompanion<T extends UpdateCompanion'
+        '<${table.dartTypeName}>>('
+        'bool nullToAbsent) {\n return $companionClass(');
 
     for (var column in table.columns) {
       final getter = column.dartGetterName;
       buffer.write('$getter: $getter == null && nullToAbsent ? '
           'const Value.absent() : Value.use($getter),');
     }
-    buffer.write(');}\n');
+    buffer.write(') as T;}\n');
   }
 
   /// Recursively creates the implementation for hashCode of the data class,
diff --git a/moor_generator/lib/src/writer/table_writer.dart b/moor_generator/lib/src/writer/table_writer.dart
index e042c87c..787318d7 100644
--- a/moor_generator/lib/src/writer/table_writer.dart
+++ b/moor_generator/lib/src/writer/table_writer.dart
@@ -79,16 +79,18 @@ class TableWriter {
   }
 
   void _writeReverseMappingMethod(StringBuffer buffer) {
-    // Map<String, Variable> entityToSql(User d, {bool includeNulls = false) {
+    // Map<String, Variable> entityToSql(covariant UpdateCompanion<D> instance)
     buffer
       ..write('@override\nMap<String, Variable> entityToSql('
-          '${table.dartTypeName} d, {bool includeNulls = false}) {\n')
+          '${table.updateCompanionName} d) {\n')
       ..write('final map = <String, Variable> {};');
 
     for (var column in table.columns) {
       buffer.write('''
-        if (d.${column.dartGetterName} != null || includeNulls) {
-          map['${column.name.name}'] = Variable<${column.dartTypeName}, ${column.sqlTypeName}>(d.${column.dartGetterName});
+        if (d.${column.dartGetterName}.present) {
+          map['${column.name.name}'] = 
+             Variable<${column.dartTypeName}, ${column.sqlTypeName}>(
+                d.${column.dartGetterName}.value);
         }
       ''');
     }
diff --git a/moor_generator/lib/src/writer/update_companion_writer.dart b/moor_generator/lib/src/writer/update_companion_writer.dart
index 348833f1..a6861bfd 100644
--- a/moor_generator/lib/src/writer/update_companion_writer.dart
+++ b/moor_generator/lib/src/writer/update_companion_writer.dart
@@ -9,7 +9,7 @@ class UpdateCompanionWriter {
 
   void writeInto(StringBuffer buffer) {
     buffer.write('class ${table.updateCompanionName} '
-        'implements UpdateCompanion<${table.dartTypeName}> {\n');
+        'extends UpdateCompanion<${table.dartTypeName}> {\n');
     _writeFields(buffer);
     _writeConstructor(buffer);
     _writeIsPresentOverride(buffer);