diff --git a/block.c b/block.c
index d79a52ca74..5ec1a3897e 100644
--- a/block.c
+++ b/block.c
@@ -5750,7 +5750,7 @@ exit:
  * sums the size of all data-bearing children.  (This excludes backing
  * children.)
  */
-static int64_t bdrv_sum_allocated_file_size(BlockDriverState *bs)
+static int64_t coroutine_fn bdrv_sum_allocated_file_size(BlockDriverState *bs)
 {
     BdrvChild *child;
     int64_t child_size, sum = 0;