add missing #define

1 files changed, 1 insertions, 0 deletions

diff --git a/getopt.c b/getopt.c
index 5f6baaa..2f1d355 100644
--- a/getopt.c
+++ b/getopt.c
@@ -1,3 +1,4 @@
+#define _POSIX_C_SOURCE 2
 #include <sys/types.h>
 #include <string.h>
 #include <stdio.h>