diff -up src/ziptool.c.old src/ziptool.c
--- src/ziptool.c.old	2016-01-28 14:19:37.026356371 +0100
+++ src/ziptool.c	2016-01-28 14:19:43.394384005 +0100
@@ -53,6 +53,7 @@
 #include "compat.h"
 
 zip_source_t *source_hole_create(const char *, int flags, zip_error_t *);
+extern int optopt;
 
 typedef enum {
     SOURCE_TYPE_NONE,