diff --git a/sys/security/mac_portacl/mac_portacl.c b/sys/security/mac_portacl/mac_portacl.c
index 64fa2ad350ce..917a6d3ee012 100644
--- a/sys/security/mac_portacl/mac_portacl.c
+++ b/sys/security/mac_portacl/mac_portacl.c
@@ -76,6 +76,7 @@
 #include <sys/socket.h>
 #include <sys/socketvar.h>
 #include <sys/stdint.h>
+#include <sys/sx.h>
 #include <sys/sysctl.h>
 
 #include <netinet/in.h>