diff --git a/web3.js/src/instruction.ts b/web3.js/src/instruction.ts
index 4162143939..4097211a50 100644
--- a/web3.js/src/instruction.ts
+++ b/web3.js/src/instruction.ts
@@ -3,21 +3,28 @@ import * as BufferLayout from '@solana/buffer-layout';
 
 import * as Layout from './layout';
 
+export interface IInstructionInputData {
+  readonly instruction: number;
+}
+
 /**
  * @internal
  */
-export type InstructionType = {
+export type InstructionType<TInputData extends IInstructionInputData> = {
   /** The Instruction index (from solana upstream program) */
   index: number;
   /** The BufferLayout to use to build data */
-  layout: BufferLayout.Layout;
+  layout: BufferLayout.Layout<TInputData>;
 };
 
 /**
  * Populate a buffer of instruction data using an InstructionType
  * @internal
  */
-export function encodeData(type: InstructionType, fields?: any): Buffer {
+export function encodeData<TInputData extends IInstructionInputData>(
+  type: InstructionType<TInputData>,
+  fields?: any,
+): Buffer {
   const allocLength =
     type.layout.span >= 0 ? type.layout.span : Layout.getAlloc(type, fields);
   const data = Buffer.alloc(allocLength);
@@ -30,8 +37,11 @@ export function encodeData(type: InstructionType, fields?: any): Buffer {
  * Decode instruction data buffer using an InstructionType
  * @internal
  */
-export function decodeData(type: InstructionType, buffer: Buffer): any {
-  let data;
+export function decodeData<TInputData extends IInstructionInputData>(
+  type: InstructionType<TInputData>,
+  buffer: Buffer,
+): TInputData {
+  let data: TInputData;
   try {
     data = type.layout.decode(buffer);
   } catch (err) {