diff --git a/src/ngircd/conn.c b/src/ngircd/conn.c
index ab975b31..0ff6067f 100644
--- a/src/ngircd/conn.c
+++ b/src/ngircd/conn.c
@@ -37,6 +37,7 @@
 #include <netinet/in.h>
 
 #ifdef HAVE_NETINET_IP_H
+# include <netinet/in_systm.h>
 # include <netinet/ip.h>
 #endif