diff --git a/indra/llwindow/llwindowwin32.cpp b/indra/llwindow/llwindowwin32.cpp
index 42ec4ee29dd0b2b426b738db4981872613cb6716..057d7a700e4f246df7392613f0d2799b7db30330 100644
--- a/indra/llwindow/llwindowwin32.cpp
+++ b/indra/llwindow/llwindowwin32.cpp
@@ -1929,7 +1929,7 @@ void LLWindowWin32::toggleVSync(bool enable_vsync)
         LL_INFOS("Window") << "Disabling vertical sync" << LL_ENDL;
         wglSwapIntervalEXT(0);
     }
-    else
+    else if (wglSwapIntervalEXT)
     {
         LL_INFOS("Window") << "Enabling vertical sync" << LL_ENDL;
         wglSwapIntervalEXT(1);