diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index 78c11d4948..100398c565 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -1519,12 +1519,10 @@ int qcow2_discard_clusters(BlockDriverState *bs, uint64_t offset,
 
     end_offset = offset + (nb_sectors << BDRV_SECTOR_BITS);
 
-    /* Round start up and end down */
-    offset = align_offset(offset, s->cluster_size);
-    end_offset = start_of_cluster(s, end_offset);
-
-    if (offset > end_offset) {
-        return 0;
+    /* The caller must cluster-align start; round end down except at EOF */
+    assert(QEMU_IS_ALIGNED(offset, s->cluster_size));
+    if (end_offset != bs->total_sectors * BDRV_SECTOR_SIZE) {
+        end_offset = start_of_cluster(s, end_offset);
     }
 
     nb_clusters = size_to_clusters(s, end_offset - offset);