diff --git a/ftepp.c b/ftepp.c
index b8fc9f4..de5022a 100644
--- a/ftepp.c
+++ b/ftepp.c
@@ -1256,7 +1256,19 @@ bool ftepp_preprocess_string(const char *name, const char *str)
 bool ftepp_init()
 {
     ftepp = ftepp_new();
-    return !!ftepp;
+    if (!ftepp)
+        return false;
+    ftepp_add_define(NULL, "GMQCC");
+    return true;
+}
+
+void ftepp_add_define(const char *source, const char *name)
+{
+    ppmacro *macro;
+    lex_ctx ctx = { "__builtin__", 0 };
+    ctx.file = source;
+    macro = ppmacro_new(ctx, name);
+    vec_push(ftepp->macros, macro);
 }
 
 const char *ftepp_get()
diff --git a/gmqcc.h b/gmqcc.h
index 8171da3..dc3de39 100644
--- a/gmqcc.h
+++ b/gmqcc.h
@@ -804,6 +804,7 @@ bool ftepp_preprocess_string(const char *name, const char *str);
 void ftepp_finish           ();
 const char *ftepp_get       ();
 void ftepp_flush            ();
+void ftepp_add_define       (const char *source, const char *name);
 
 /*===================================================================*/
 /*======================= main.c commandline ========================*/