diff --git a/mini_httpd.c b/mini_httpd.c
index 72fee8d..f382d2e 100644
--- a/mini_httpd.c
+++ b/mini_httpd.c
@@ -52,6 +52,7 @@
 #include <arpa/inet.h>
 #include <netdb.h>
 #include <dirent.h>
+#include <grp.h>	/* initgroups() */
 
 #include "port.h"
 #include "match.h"