diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index 5727f92dcb..21884a1ab9 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -513,7 +513,8 @@ static int coroutine_fn do_perform_cow_read(BlockDriverState *bs,
      */
     assert(src_cluster_offset <= INT64_MAX);
     assert(src_cluster_offset + offset_in_cluster <= INT64_MAX);
-    assert(qiov->size <= INT64_MAX);
+    /* Cast qiov->size to uint64_t to silence a compiler warning on -m32 */
+    assert((uint64_t)qiov->size <= INT64_MAX);
     bdrv_check_qiov_request(src_cluster_offset + offset_in_cluster, qiov->size,
                             qiov, 0, &error_abort);
     /*