diff --git a/migration/block.c b/migration/block.c
index b9580a6c7e..86c2256a2b 100644
--- a/migration/block.c
+++ b/migration/block.c
@@ -368,7 +368,9 @@ static void unset_dirty_tracking(void)
     BlkMigDevState *bmds;
 
     QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
-        bdrv_release_dirty_bitmap(bmds->dirty_bitmap);
+        if (bmds->dirty_bitmap) {
+            bdrv_release_dirty_bitmap(bmds->dirty_bitmap);
+        }
     }
 }
 
@@ -676,13 +678,18 @@ static int64_t get_remaining_dirty(void)
 static void block_migration_cleanup_bmds(void)
 {
     BlkMigDevState *bmds;
+    BlockDriverState *bs;
     AioContext *ctx;
 
     unset_dirty_tracking();
 
     while ((bmds = QSIMPLEQ_FIRST(&block_mig_state.bmds_list)) != NULL) {
         QSIMPLEQ_REMOVE_HEAD(&block_mig_state.bmds_list, entry);
-        bdrv_op_unblock_all(blk_bs(bmds->blk), bmds->blocker);
+
+        bs = blk_bs(bmds->blk);
+        if (bs) {
+            bdrv_op_unblock_all(bs, bmds->blocker);
+        }
         error_free(bmds->blocker);
 
         /* Save ctx, because bmds->blk can disappear during blk_unref.  */