diff --git a/Misc/NEWS b/Misc/NEWS
index 8b1d085a3d5..5a16b8b4c52 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -364,6 +364,10 @@ Extension modules
   loop in the search function, once the pointer exceeded the buffer
   limit.
 
+- The os.fdopen function now enforces a file mode starting with the
+  letter 'r', 'w' or 'a', otherwise a ValueError is raised. This fixes
+  bug #623464.
+
 Library
 -------