diff --git a/core/ISmmPluginExt.h b/core/ISmmPluginExt.h
index 8fb222c..968ed66 100644
--- a/core/ISmmPluginExt.h
+++ b/core/ISmmPluginExt.h
@@ -63,6 +63,7 @@
 #define SOURCE_ENGINE_MOCK				25				/**< Mock source engine */
 #define SOURCE_ENGINE_PVKII				26				/**< Pirates, Vikings, and Knights II */
 #define SOURCE_ENGINE_MCV				27				/**< Military Conflict: Vietnam */
+#define SOURCE_ENGINE_CS2				28				/**< Counter-Strike 2 */
 
 #define METAMOD_PLAPI_VERSION			16				/**< Version of this header file */
 #define METAMOD_PLAPI_NAME				"ISmmPlugin"	/**< Name of the plugin interface */