--- zlib-1.2.3/gzio.c.orig	2005-07-11 20:31:48 +0000

+++ zlib-1.2.3/gzio.c	2005-07-02 15:37:21 +0000

@@ -588,6 +588,9 @@ int ZEXPORT gzwrite (file, buf, len)

     }

     s->crc = crc32(s->crc, (const Bytef *)buf, len);

+    if (len == s->stream.avail_in &&

+        (s->z_err == Z_DATA_ERROR || s->z_err == Z_ERRNO))

+        return -1;

     return (int)(len - s->stream.avail_in);

 }