diff --git a/peps/pep-0007.rst b/peps/pep-0007.rst
index bcad808ee8e..fd7b48218b8 100644
--- a/peps/pep-0007.rst
+++ b/peps/pep-0007.rst
@@ -31,7 +31,12 @@ C dialect
 
 * Python 3.11 and newer versions use C11 without `optional features
   <https://en.wikipedia.org/wiki/C11_%28C_standard_revision%29#Optional_features>`_.
-  The public C API should be compatible with C++.
+
+* The public C API should be compatible with C99 and with C++03.
+
+  The existing API does use a few C11 features which are
+  commonly available as compiler extensions to C99.
+  New API should not use these features.
 
 * Python 3.6 to 3.10 use C89 with several select C99 features: