diff --git a/glx/glxcmds.c b/glx/glxcmds.c
index 1c88c2a06..a8bfe30ef 100644
--- a/glx/glxcmds.c
+++ b/glx/glxcmds.c
@@ -133,7 +133,8 @@ validGlxFBConfigForWindow(ClientPtr client, __GLXconfig * config,
     BUG_RETURN_VAL(!pVisual, FALSE);
 
     /* FIXME: What exactly should we check here... */
-    if (pVisual->class != glxConvertToXVisualType(config->visualType) ||
+    if (pVisual == NULL ||
+        pVisual->class != glxConvertToXVisualType(config->visualType) ||
         !(config->drawableType & GLX_WINDOW_BIT)) {
         client->errorValue = pDraw->id;
         *err = BadMatch;