diff --git a/block/qcow2-cluster.c b/block/qcow2-cluster.c
index f94183529c3c605db5c7bfadb9126411043cb4ad..9ba2d7133380cc818a38dfd7ac8b81a52472af16 100644
--- a/block/qcow2-cluster.c
+++ b/block/qcow2-cluster.c
@@ -427,7 +427,7 @@ static int coroutine_fn do_perform_cow(BlockDriverState *bs,
 
     if (bs->encrypted) {
         Error *err = NULL;
-        int64_t sector = (cluster_offset + offset_in_cluster)
+        int64_t sector = (src_cluster_offset + offset_in_cluster)
                          >> BDRV_SECTOR_BITS;
         assert(s->cipher);
         assert((offset_in_cluster & ~BDRV_SECTOR_MASK) == 0);
diff --git a/tests/qemu-iotests/158 b/tests/qemu-iotests/158
new file mode 100755
index 0000000000000000000000000000000000000000..a6cdd6d8cfa5822d614743d0066b761478f39fa0
--- /dev/null
+++ b/tests/qemu-iotests/158
@@ -0,0 +1,80 @@
+#!/bin/bash
+#
+# Test encrypted read/write using backing files
+#
+# Copyright (C) 2015 Red Hat, Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+# creator
+owner=berrange@redhat.com
+
+seq=`basename $0`
+echo "QA output created by $seq"
+
+here=`pwd`
+status=1	# failure is the default!
+
+_cleanup()
+{
+	_cleanup_test_img
+}
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+# get standard environment, filters and checks
+. ./common.rc
+. ./common.filter
+
+_supported_fmt qcow2
+_supported_proto generic
+_supported_os Linux
+
+
+size=128M
+TEST_IMG_BASE=$TEST_IMG.base
+
+TEST_IMG_SAVE=$TEST_IMG
+TEST_IMG=$TEST_IMG_BASE
+echo "== create base =="
+IMGOPTS="encryption=on" _make_test_img $size
+TEST_IMG=$TEST_IMG_SAVE
+
+echo
+echo "== writing whole image =="
+echo "astrochicken" | $QEMU_IO -c "write -P 0xa 0 $size" "$TEST_IMG_BASE" | _filter_qemu_io | _filter_testdir
+
+echo
+echo "== verify pattern =="
+echo "astrochicken" | $QEMU_IO -c "read -P 0xa 0 $size" "$TEST_IMG_BASE" | _filter_qemu_io | _filter_testdir
+
+echo "== create overlay =="
+IMGOPTS="encryption=on" _make_test_img -b "$TEST_IMG_BASE" $size
+
+echo
+echo "== writing part of a cluster =="
+echo "astrochicken" | $QEMU_IO -c "write -P 0xe 0 1024" "$TEST_IMG" | _filter_qemu_io | _filter_testdir
+
+echo
+echo "== verify pattern =="
+echo "astrochicken" | $QEMU_IO -c "read -P 0xe 0 1024" "$TEST_IMG" | _filter_qemu_io | _filter_testdir
+echo
+echo "== verify pattern =="
+echo "astrochicken" | $QEMU_IO -c "read -P 0xa 1024 64512" "$TEST_IMG" | _filter_qemu_io | _filter_testdir
+
+
+# success, all done
+echo "*** done"
+rm -f $seq.full
+status=0
diff --git a/tests/qemu-iotests/158.out b/tests/qemu-iotests/158.out
new file mode 100644
index 0000000000000000000000000000000000000000..b3f37e28eff4345e0e1f86f7ee08bdec88e4d129
--- /dev/null
+++ b/tests/qemu-iotests/158.out
@@ -0,0 +1,36 @@
+QA output created by 158
+== create base ==
+Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134217728 encryption=on
+
+== writing whole image ==
+Disk image 'TEST_DIR/t.qcow2.base' is encrypted.
+password:
+wrote 134217728/134217728 bytes at offset 0
+128 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+== verify pattern ==
+Disk image 'TEST_DIR/t.qcow2.base' is encrypted.
+password:
+read 134217728/134217728 bytes at offset 0
+128 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+== create overlay ==
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base encryption=on
+
+== writing part of a cluster ==
+Disk image 'TEST_DIR/t.qcow2' is encrypted.
+password:
+wrote 1024/1024 bytes at offset 0
+1 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+== verify pattern ==
+Disk image 'TEST_DIR/t.qcow2' is encrypted.
+password:
+read 1024/1024 bytes at offset 0
+1 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+== verify pattern ==
+Disk image 'TEST_DIR/t.qcow2' is encrypted.
+password:
+read 64512/64512 bytes at offset 1024
+63 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+*** done
diff --git a/tests/qemu-iotests/group b/tests/qemu-iotests/group
index 50ddeed80a0d003384550ad0d0e38258be9d829a..ad3518db58adc793f5ed0cc278fa9d898ae89b54 100644
--- a/tests/qemu-iotests/group
+++ b/tests/qemu-iotests/group
@@ -157,4 +157,5 @@
 155 rw auto
 156 rw auto quick
 157 auto
+158 rw auto quick
 162 auto quick