diff --git a/sys/dev/drm/drm_os_freebsd.h b/sys/dev/drm/drm_os_freebsd.h
index 491c5c06959c..c2bb845c4ee5 100644
--- a/sys/dev/drm/drm_os_freebsd.h
+++ b/sys/dev/drm/drm_os_freebsd.h
@@ -4,6 +4,7 @@
 
 #include <sys/param.h>
 #include <sys/queue.h>
+#include <sys/lockmgr.h>
 #include <sys/malloc.h>
 #include <sys/kernel.h>
 #include <sys/module.h>