--- main.c.old	2017-12-26 18:09:07.383869000 -0500
+++ main.c	2017-12-26 18:08:13.470618500 -0500
@@ -20,6 +20,7 @@
     corrupt or invalid input file, 3 for an internal consistency error
     (eg, bug) which caused clzip to panic.
 */
+#define _XOPEN_SOURCE 500
 
 #define _FILE_OFFSET_BITS 64
 #include <ctype.h>