diff --git a/misc/ssfilter.y b/misc/ssfilter.y
index f47ab2fd..8be53680 100644
--- a/misc/ssfilter.y
+++ b/misc/ssfilter.y
@@ -1,6 +1,7 @@
 %{
 
 #include <stdio.h>
+#include <stdlib.h>
 #include <malloc.h>
 #include <string.h>
 #include "ssfilter.h"