diff --git a/indra/newview/llviewercontrol.cpp b/indra/newview/llviewercontrol.cpp
index c56646b30f21d7f3e4fc7a9892373129bf6da596..a15a4531f532f175842df369ef03d2a86ba1f8ca 100644
--- a/indra/newview/llviewercontrol.cpp
+++ b/indra/newview/llviewercontrol.cpp
@@ -265,7 +265,10 @@ static bool validateAnisotropicFiltering(const LLSD& val)
 static bool handleVSyncChanged(const LLSD& newvalue)
 {
     LLPerfStats::tunables.vsyncEnabled = newvalue.asBoolean();
-    gViewerWindow->getWindow()->toggleVSync(newvalue.asBoolean());
+    if (gViewerWindow && gViewerWindow->getWindow())
+    {
+        gViewerWindow->getWindow()->toggleVSync(newvalue.asBoolean());
+    }
 
     if(newvalue.asBoolean() == true)
     {