diff --git a/flang/documentation/Extensions.md b/flang/documentation/Extensions.md
index 6bb054927535..f0a2e6c40826 100644
--- a/flang/documentation/Extensions.md
+++ b/flang/documentation/Extensions.md
@@ -90,3 +90,4 @@ Extensions and legacy features deliberately not supported
 * `Z` prefix on unquoted hexadecimal constants (dangerous)
 * `T` and `F` as abbreviations for `.TRUE.` and `.FALSE.` (dangerous)
 * Use of host FORMAT labels in internal subprograms (PGI-only feature)
+* ALLOCATE(TYPE(derived)::...) as variant of correct ALLOCATE(derived::...) (PGI only)