diff --git a/sys/vm/vm_pageout.c b/sys/vm/vm_pageout.c
index e0d00f5172f..5611ae66694 100644
--- a/sys/vm/vm_pageout.c
+++ b/sys/vm/vm_pageout.c
@@ -1174,11 +1174,12 @@ unlock_page:
 		queues_locked = FALSE;
 
 		/*
-		 * Invalid pages can be easily freed. They cannot be
-		 * mapped, vm_page_free() asserts this.
+		 * Invalid pages cannot appear on a queue.  If
+		 * vm_pageout_fallback_object_lock() allowed a window
+		 * where the page could be invalidated, it should
+		 * detect this.
 		 */
-		if (m->valid == 0)
-			goto free_page;
+		KASSERT(m->valid != 0, ("Invalid page %p on inact queue", m));
 
 		/*
 		 * If the page has been referenced and the object is not dead,
@@ -1231,7 +1232,6 @@ unlock_page:
 			/*
 			 * Clean pages can be freed.
 			 */
-free_page:
 			vm_page_free(m);
 			PCPU_INC(cnt.v_dfree);
 			--page_shortage;