diff --git a/contrib/unzip/unzip.c b/contrib/unzip/unzip.c
index e8b62e763..fea6e8913 100644
--- a/contrib/unzip/unzip.c
+++ b/contrib/unzip/unzip.c
@@ -41,6 +41,10 @@ woven in by Terry Thorsen 1/2003.
 #include "zlib.h"
 #include "unzip.h"
 
+#if ZLIB_VERNUM < 0x1270
+typedef unsigned long z_crc_t;
+#endif
+
 #ifdef STDC
 #  include <stddef.h>
 #  include <string.h>