diff --git a/sys/net/pfil.h b/sys/net/pfil.h
index ccf7a651717a..6b00e5c5f0d9 100644
--- a/sys/net/pfil.h
+++ b/sys/net/pfil.h
@@ -36,6 +36,7 @@
 #include <sys/queue.h>
 #include <sys/_lock.h>
 #include <sys/_mutex.h>
+#include <sys/lock.h>
 #include <sys/rwlock.h>
 
 struct mbuf;