diff --git a/win32ss/user/ntuser/class.c b/win32ss/user/ntuser/class.c
index 2bda75012d6..83fe9009b34 100644
--- a/win32ss/user/ntuser/class.c
+++ b/win32ss/user/ntuser/class.c
@@ -2706,6 +2706,10 @@ NtUserGetClassInfo(
     {
         ProbeForWrite( lpWndClassEx, sizeof(WNDCLASSEXW), sizeof(ULONG));
         RtlCopyMemory( &Safewcexw, lpWndClassEx, sizeof(WNDCLASSEXW));
+        if (ppszMenuName)
+        {
+            ProbeForWrite(ppszMenuName, sizeof(*ppszMenuName), sizeof(PVOID));
+        }
     }
     _SEH2_EXCEPT(EXCEPTION_EXECUTE_HANDLER)
     {