diff --git a/sys/vm/vm_page.c b/sys/vm/vm_page.c
index 540dadf65842..449b299c7338 100644
--- a/sys/vm/vm_page.c
+++ b/sys/vm/vm_page.c
@@ -757,6 +757,7 @@ vm_page_sunbusy(vm_page_t m)
 {
 	u_int x;
 
+	vm_page_lock_assert(m, MA_NOTOWNED);
 	vm_page_assert_sbusied(m);
 
 	for (;;) {