diff --git a/zutil.c b/zutil.c
index 3b4d904..56534fb 100644
--- a/zutil.c
+++ b/zutil.c
@@ -113,7 +113,7 @@
 }
 
 #ifdef ZLIB_DEBUG
-
+#include <stdlib.h>
 #  ifndef verbose
 #    define verbose 0
 #  endif