diff --git a/sys/kern/kern_synch.c b/sys/kern/kern_synch.c
index 7c9b50bf52f6..7d9877501b92 100644
--- a/sys/kern/kern_synch.c
+++ b/sys/kern/kern_synch.c
@@ -47,6 +47,7 @@
 #include <sys/ipl.h>
 #include <sys/kernel.h>
 #include <sys/ktr.h>
+#include <sys/lock.h>
 #include <sys/mutex.h>
 #include <sys/signalvar.h>
 #include <sys/resourcevar.h>