diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c
index 362deaf303..6b8b63514a 100644
--- a/block/qcow2-refcount.c
+++ b/block/qcow2-refcount.c
@@ -839,6 +839,13 @@ static int QEMU_WARN_UNUSED_RESULT update_refcount(BlockDriverState *bs,
                 qcow2_cache_put(s->refcount_block_cache, &refcount_block);
             }
             ret = alloc_refcount_block(bs, cluster_index, &refcount_block);
+            /* If the caller needs to restart the search for free clusters,
+             * try the same ones first to see if they're still free. */
+            if (ret == -EAGAIN) {
+                if (s->free_cluster_index > (start >> s->cluster_bits)) {
+                    s->free_cluster_index = (start >> s->cluster_bits);
+                }
+            }
             if (ret < 0) {
                 goto fail;
             }
diff --git a/tests/qemu-iotests/026.out b/tests/qemu-iotests/026.out
index 86a50a2e13..8e89416a86 100644
--- a/tests/qemu-iotests/026.out
+++ b/tests/qemu-iotests/026.out
@@ -533,7 +533,7 @@ Failed to flush the L2 table cache: No space left on device
 Failed to flush the refcount block cache: No space left on device
 write failed: No space left on device
 
-11 leaked clusters were found on the image.
+10 leaked clusters were found on the image.
 This means waste of disk space, but no harm to data.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
@@ -561,7 +561,7 @@ Failed to flush the L2 table cache: No space left on device
 Failed to flush the refcount block cache: No space left on device
 write failed: No space left on device
 
-11 leaked clusters were found on the image.
+10 leaked clusters were found on the image.
 This means waste of disk space, but no harm to data.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
@@ -589,7 +589,7 @@ Failed to flush the L2 table cache: No space left on device
 Failed to flush the refcount block cache: No space left on device
 write failed: No space left on device
 
-11 leaked clusters were found on the image.
+10 leaked clusters were found on the image.
 This means waste of disk space, but no harm to data.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824
 
diff --git a/tests/qemu-iotests/121 b/tests/qemu-iotests/121
index 1307b4e327..6d6f55a5dc 100755
--- a/tests/qemu-iotests/121
+++ b/tests/qemu-iotests/121
@@ -93,6 +93,26 @@ $QEMU_IO -c 'write 63M 130K' "$TEST_IMG" | _filter_qemu_io
 
 _check_test_img
 
+echo
+echo '=== Allocating a new refcount block must not leave holes in the image ==='
+echo
+
+IMGOPTS='cluster_size=512,refcount_bits=16' _make_test_img 1M
+
+# This results in an image with 256 used clusters: the qcow2 header,
+# the refcount table, one refcount block, the L1 table, four L2 tables
+# and 248 data clusters
+$QEMU_IO -c 'write 0 124k' "$TEST_IMG" | _filter_qemu_io
+
+# 256 clusters of 512 bytes each give us a 128K image
+stat -c "size=%s (expected 131072)" $TEST_IMG
+
+# All 256 entries of the refcount block are used, so writing a new
+# data cluster also allocates a new refcount block
+$QEMU_IO -c 'write 124k 512' "$TEST_IMG" | _filter_qemu_io
+
+# Two more clusters, the image size should be 129K now
+stat -c "size=%s (expected 132096)" $TEST_IMG
 
 # success, all done
 echo
diff --git a/tests/qemu-iotests/121.out b/tests/qemu-iotests/121.out
index 5961a44cd9..613d56185e 100644
--- a/tests/qemu-iotests/121.out
+++ b/tests/qemu-iotests/121.out
@@ -20,4 +20,14 @@ wrote 133120/133120 bytes at offset 66060288
 130 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 No errors were found on the image.
 
+=== Allocating a new refcount block must not leave holes in the image ===
+
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1048576
+wrote 126976/126976 bytes at offset 0
+124 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+size=131072 (expected 131072)
+wrote 512/512 bytes at offset 126976
+512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+size=132096 (expected 132096)
+
 *** done