diff --git a/sig-client.c b/sig-client.c
index 7a20af1..057b17c 100644
--- a/sig-client.c
+++ b/sig-client.c
@@ -1,7 +1,7 @@
 #define _XOPEN_SOURCE 500
 #include <stdio.h>
 #include <signal.h>
-#include <getopt.h>
+#include <unistd.h>
 #include <sys/types.h>
 
 void printUsage(char *arg);