diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index fedcf57..c016e85 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -763,6 +763,11 @@ int qcow2_alloc_cluster_link_l2(BlockDriverState *bs, QCowL2Meta *m)
     for (i = 0; i < m->nb_clusters; i++) {
         uint64_t flags = 0;
         uint64_t offset = cluster_offset + (i << s->cluster_bits);
+
+        if (be64_to_cpu(l2_table[l2_index + i]) == offset) {
+            continue;
+        }
+
         /* if two concurrent writes happen to the same unallocated cluster
 	 * each write allocates separate cluster and writes data concurrently.
 	 * The first one to complete updates l2 table with pointer to its