diff --git a/extensions/sdktools/extension.h b/extensions/sdktools/extension.h
index 37bf6dac..43438806 100644
--- a/extensions/sdktools/extension.h
+++ b/extensions/sdktools/extension.h
@@ -44,7 +44,7 @@
 #include <IGameHelpers.h>
 #include <IEngineTrace.h>
 #include <IEngineSound.h>
-#include <IVoiceServer.h>
+#include <ivoiceserver.h>
 #include <convar.h>
 
 /**