diff --git a/data/c.m4 b/data/c.m4
index 994d2964..561900af 100644
--- a/data/c.m4
+++ b/data/c.m4
@@ -602,7 +602,7 @@ m4_define([b4_YYDEBUG_define],
 #  endif
 # else /* ! defined YYDEBUG */
 #  define ]b4_api_PREFIX[DEBUG ]b4_debug_flag[
-# endif /* ! defined ]b4_api_PREFIX[DEBUG */
+# endif /* ! defined YYDEBUG */
 #endif  /* ! defined ]b4_api_PREFIX[DEBUG */]])[]dnl
 ])