--- a/sys/dev/drm/ttm/ttm_page_alloc.c
+++ b/sys/dev/drm/ttm/ttm_page_alloc.c
@@ -398,6 +398,8 @@
 	sc->gfp_mask = M_WAITOK;
 #endif
 
+	if (_manager == NULL)
+		return SHRINK_STOP;
 	if (!mutex_trylock(&lock))
 		return SHRINK_STOP;
 	pool_offset = ++start_pool % NUM_POOLS;