diff --git a/Mac/mwerks/mwerks_plugin_config.h b/Mac/mwerks/mwerks_plugin_config.h
index 4e23a64..785883a 100644
--- a/Mac/mwerks/mwerks_plugin_config.h
+++ b/Mac/mwerks/mwerks_plugin_config.h
@@ -4,6 +4,9 @@
 
 /* #define USE_GUSI1		/* Stdio implemented with GUSI */
 #define USE_GUSI2		/* Stdio implemented with GUSI */
+#if defined(USE_GUSI1) || defined(USE_GUSI2)
+#define USE_GUSI
+#endif
 #define WITH_THREAD		/* Use thread support (needs GUSI 2, not GUSI 1) */
 #define USE_MSL			/* Use MSL libraries */
 #ifdef USE_MSL