diff --git a/sys/sys/mutex.h b/sys/sys/mutex.h
--- a/sys/sys/mutex.h
+++ b/sys/sys/mutex.h
@@ -38,6 +38,10 @@
 #include <sys/_lock.h>
 #include <sys/_mutex.h>
 
+#if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
+#include <sys/lock.h>
+#endif
+
 #ifdef _KERNEL
 #include <sys/pcpu.h>
 #include <sys/lock_profile.h>