diff --git a/src/Conn.h b/src/Conn.h
index e078c763d7..ee6bcd90b3 100644
--- a/src/Conn.h
+++ b/src/Conn.h
@@ -5,6 +5,7 @@
 
 #include "bro-config.h"
 
+#include <sys/types.h>
 #ifdef HAVE_NETINET_ETHER_H
 #include <netinet/ether.h>
 #endif