diff --git a/tcpslice-1.2a3/util.c b/tcpslice-1.2a3/util.c
index cebaa5b..cada4c1 100644
--- a/tcpslice-1.2a3/util.c
+++ b/tcpslice-1.2a3/util.c
@@ -27,6 +27,7 @@ static const char rcsid[] =
 #include <sys/types.h>
 
 #include <stdio.h>
+#include <stdlib.h>
 #if __STDC__
 #include <stdarg.h>
 #else