diff --git a/block.c b/block.c
index 1d37f133a8..3e277855e7 100644
--- a/block.c
+++ b/block.c
@@ -4866,7 +4866,7 @@ static int bdrv_replace_node_common(BlockDriverState *from,
     Transaction *tran = tran_new();
     g_autoptr(GHashTable) found = NULL;
     g_autoptr(GSList) refresh_list = NULL;
-    BlockDriverState *to_cow_parent;
+    BlockDriverState *to_cow_parent = NULL;
     int ret;
 
     if (detach_subchain) {