diff --git a/src/video/x11/SDL_x11messagebox.c b/src/video/x11/SDL_x11messagebox.c
index 489689692e..64d4938c69 100644
--- a/src/video/x11/SDL_x11messagebox.c
+++ b/src/video/x11/SDL_x11messagebox.c
@@ -250,11 +250,11 @@ static bool X11_ShowMessageBoxImpl(const SDL_MessageBoxData *messageboxdata, int
 #else 
     controls.window = X11Toolkit_CreateWindowStruct(parent_window, NULL, SDL_TOOLKIT_WINDOW_MODE_X11_DIALOG, colorhints, false);
 #endif
-    controls.window->cb_data = &controls;
-    controls.window->cb_on_scale_change = X11_OnMessageBoxScaleChange;
     if (!controls.window) {
         return false;
     }
+    controls.window->cb_data = &controls;
+    controls.window->cb_on_scale_change = X11_OnMessageBoxScaleChange;
 
     /* Create controls */
     controls.buttonID = buttonID;