diff --git a/contrib/unzip/crypt.h b/contrib/unzip/crypt.h
index e627b3bee..78146eb83 100644
--- a/contrib/unzip/crypt.h
+++ b/contrib/unzip/crypt.h
@@ -17,8 +17,10 @@
 #define _MINICRYPT_H
 
 #if ZLIB_VERNUM < 0x1270
+#if !defined(Z_U4)
 typedef unsigned long z_crc_t;
 #endif
+#endif
 
 #ifdef __cplusplus
 extern "C" {