diff --git a/src/video/win32/SDL_win32window.c b/src/video/win32/SDL_win32window.c
index d69ba6a63..2b8c75fe8 100644
--- a/src/video/win32/SDL_win32window.c
+++ b/src/video/win32/SDL_win32window.c
@@ -115,7 +115,9 @@ SetupWindowData(_THIS, SDL_Window * window, HWND hwnd, SDL_bool created)
     if (data->wndproc == WIN_WindowProc) {
         data->wndproc = NULL;
     }
-    SetWindowLongPtr(hwnd, GWLP_WNDPROC, (LONG_PTR) WIN_WindowProc);
+    else {
+        SetWindowLongPtr(hwnd, GWLP_WNDPROC, (LONG_PTR) WIN_WindowProc);
+    }
 
     /* Fill in the SDL window with the window data */
     {