diff --git a/code/tools/lcc/lburg/gram.y b/code/tools/lcc/lburg/gram.y
index 1ecd8a9e..c0a9c942 100644
--- a/code/tools/lcc/lburg/gram.y
+++ b/code/tools/lcc/lburg/gram.y
@@ -199,4 +199,5 @@ void yywarn(char *fmt, ...) {
 		fprintf(stderr, "line %d: ", yylineno);
 	fprintf(stderr, "warning: ");
 	vfprintf(stderr, fmt, ap);
+	va_end(ap);
 }