diff --recursive --unified tl-expected-1.0.1-orig/include/tl/expected.hpp tl-expected-1.0.1/include/tl/expected.hpp
--- tl-expected-1.0.1-orig/include/tl/expected.hpp	2022-08-30 20:10:13.269489852 +0100
+++ tl-expected-1.0.1/include/tl/expected.hpp	2022-08-30 20:17:35.744258828 +0100
@@ -24,6 +24,7 @@
 #include <functional>
 #include <type_traits>
 #include <utility>
+#include <cassert>
 
 #if defined(__EXCEPTIONS) || defined(_CPPUNWIND)
 #define TL_EXPECTED_EXCEPTIONS_ENABLED
@@ -1862,27 +1863,37 @@
     }
   }
 
-  constexpr const T *operator->() const { return valptr(); }
-  TL_EXPECTED_11_CONSTEXPR T *operator->() { return valptr(); }
+  constexpr const T *operator->() const {
+    assert(has_value());
+    return valptr();
+  }
+  TL_EXPECTED_11_CONSTEXPR T *operator->() {
+    assert(has_value());
+    return valptr();
+  }
 
   template <class U = T,
             detail::enable_if_t<!std::is_void<U>::value> * = nullptr>
   constexpr const U &operator*() const & {
+    assert(has_value());
     return val();
   }
   template <class U = T,
             detail::enable_if_t<!std::is_void<U>::value> * = nullptr>
   TL_EXPECTED_11_CONSTEXPR U &operator*() & {
+    assert(has_value());
     return val();
   }
   template <class U = T,
             detail::enable_if_t<!std::is_void<U>::value> * = nullptr>
   constexpr const U &&operator*() const && {
+    assert(has_value());
     return std::move(val());
   }
   template <class U = T,
             detail::enable_if_t<!std::is_void<U>::value> * = nullptr>
   TL_EXPECTED_11_CONSTEXPR U &&operator*() && {
+    assert(has_value());
     return std::move(val());
   }
 
@@ -1918,10 +1929,22 @@
     return std::move(val());
   }
 
-  constexpr const E &error() const & { return err().value(); }
-  TL_EXPECTED_11_CONSTEXPR E &error() & { return err().value(); }
-  constexpr const E &&error() const && { return std::move(err().value()); }
-  TL_EXPECTED_11_CONSTEXPR E &&error() && { return std::move(err().value()); }
+  constexpr const E &error() const & {
+    assert(!has_value());
+    return err().value();
+  }
+  TL_EXPECTED_11_CONSTEXPR E &error() & {
+    assert(!has_value());
+    return err().value();
+  }
+  constexpr const E &&error() const && {
+    assert(!has_value());
+    return std::move(err().value());
+  }
+  TL_EXPECTED_11_CONSTEXPR E &&error() && {
+    assert(!has_value());
+    return std::move(err().value());
+  }
 
   template <class U> constexpr T value_or(U &&v) const & {
     static_assert(std::is_copy_constructible<T>::value &&