diff --git a/dlls/user32/tests/win.c b/dlls/user32/tests/win.c
index 31d14480861..a3216da9f46 100644
--- a/dlls/user32/tests/win.c
+++ b/dlls/user32/tests/win.c
@@ -7293,6 +7293,15 @@ static void test_SetWindowLong(void)
             "SetWindowLongPtr on invalid window proc shouldn't have changed the value returned by GetWindowLongPtr, instead of changing it to 0x%Ix\n", retval);
         ok(IsWindowUnicode(hwndMain), "hwndMain should now be Unicode\n");
 
+        /* Make sure nothing changes if we set the same proc */
+        retval = SetWindowLongPtrW(hwndMain, GWLP_WNDPROC, (LONG_PTR)old_window_procW);
+        todo_wine
+        ok((WNDPROC)retval == main_window_procA, "unexpected proc 0x%Ix\n", retval);
+        retval = GetWindowLongPtrW(hwndMain, GWLP_WNDPROC);
+        ok((WNDPROC)retval == old_window_procW, "unexpected proc 0x%Ix\n", retval);
+        retval = GetWindowLongPtrA(hwndMain, GWLP_WNDPROC);
+        ok((WNDPROC)retval == main_window_procA, "unexpected proc 0x%Ix\n", retval);
+
         /* set it back to ANSI */
         SetWindowLongPtrA(hwndMain, GWLP_WNDPROC, 0);
     }
diff --git a/dlls/wow64win/user.c b/dlls/wow64win/user.c
index 8065a05f44a..602ccfa79b9 100644
--- a/dlls/wow64win/user.c
+++ b/dlls/wow64win/user.c
@@ -3832,6 +3832,13 @@ NTSTATUS WINAPI wow64_NtUserSetWindowLong( UINT *args )
     LONG newval = get_ulong( &args );
     BOOL ansi = get_ulong( &args );
 
+    switch (offset)
+    {
+    case GWLP_HINSTANCE:
+    case GWLP_WNDPROC:
+        return NtUserSetWindowLongPtr( hwnd, offset, (ULONG)newval, ansi );
+    }
+
     return NtUserSetWindowLong( hwnd, offset, newval, ansi );
 }