diff --git a/docs/headers.md b/docs/headers.md
index fb9ccba..566bbbd 100644
--- a/docs/headers.md
+++ b/docs/headers.md
@@ -485,6 +485,9 @@ constexpr span(const span<OtherElementType, OtherExtent>& other) noexcept;
 Constructs a `span` from another `span`. This constructor is available if `OtherExtent == Extent || Extent ==`[`gsl::dynamic_extent`](#user-content-H-span_ext-dynamic_extent)` || OtherExtent ==`[`gsl::dynamic_extent`](#user-content-H-span_ext-dynamic_extent)
 and if `ElementType` and `OtherElementType` are compatible.
 
+If `Extent !=`[`gsl::dynamic_extent`](#user-content-H-span_ext-dynamic_extent) and `OtherExtent ==`[`gsl::dynamic_extent`](#user-content-H-span_ext-dynamic_extent),
+then the constructor [`Expects`](#user-content-H-assert-expects) that `other.size() == Extent`.
+
 ```cpp
 constexpr span& operator=(const span& other) noexcept = default;
 ```
diff --git a/tests/span_tests.cpp b/tests/span_tests.cpp
index ebff22e..efe0195 100644
--- a/tests/span_tests.cpp
+++ b/tests/span_tests.cpp
@@ -681,6 +681,13 @@ TEST(span_test, from_convertible_span_constructor)
         static_cast<void>(avcd);
     }
 
+    {
+        std::array<DerivedClass, 2> arr{};
+        span<DerivedClass> avd{arr};
+        using T = span<const DerivedClass, 1>;
+        EXPECT_DEATH(T{avd}, expected);
+    }
+
     {
         std::array<DerivedClass, 1> arr{};
         span<DerivedClass> avd{arr};