diff --git a/block/qcow2.c b/block/qcow2.c
index d44b45633d..7bb7e392e1 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -3763,6 +3763,12 @@ static coroutine_fn int qcow2_co_pdiscard(BlockDriverState *bs,
     int ret;
     BDRVQcow2State *s = bs->opaque;
 
+    /* If the image does not support QCOW_OFLAG_ZERO then discarding
+     * clusters could expose stale data from the backing file. */
+    if (s->qcow_version < 3 && bs->backing) {
+        return -ENOTSUP;
+    }
+
     if (!QEMU_IS_ALIGNED(offset | bytes, s->cluster_size)) {
         assert(bytes < s->cluster_size);
         /* Ignore partial clusters, except for the special case of the
diff --git a/tests/qemu-iotests/060 b/tests/qemu-iotests/060
index 043f12904a..4a4fdfb1e1 100755
--- a/tests/qemu-iotests/060
+++ b/tests/qemu-iotests/060
@@ -167,9 +167,10 @@ _make_test_img -o 'compat=0.10' -b "$BACKING_IMG" 1G
 # Write two clusters, the second one enforces creation of an L2 table after
 # the first data cluster.
 $QEMU_IO -c 'write 0k 64k' -c 'write 512M 64k' "$TEST_IMG" | _filter_qemu_io
-# Discard the first cluster. This cluster will soon enough be reallocated and
+# Free the first cluster. This cluster will soon enough be reallocated and
 # used for COW.
-$QEMU_IO -c 'discard 0k 64k' "$TEST_IMG" | _filter_qemu_io
+poke_file "$TEST_IMG" '262144' "\x00\x00\x00\x00\x00\x00\x00\x00" # 0x40000 - L2 entry
+poke_file "$TEST_IMG" '131082' "\x00\x00" # 0x2000a - Refcount entry
 # Now, corrupt the image by marking the second L2 table cluster as free.
 poke_file "$TEST_IMG" '131084' "\x00\x00" # 0x2000c
 # Start a write operation requiring COW on the image stopping it right before
diff --git a/tests/qemu-iotests/060.out b/tests/qemu-iotests/060.out
index d27692a33c..09caaea865 100644
--- a/tests/qemu-iotests/060.out
+++ b/tests/qemu-iotests/060.out
@@ -105,8 +105,6 @@ wrote 65536/65536 bytes at offset 0
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 wrote 65536/65536 bytes at offset 536870912
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-discard 65536/65536 bytes at offset 0
-64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 qcow2: Marking image as corrupt: Preventing invalid write on metadata (overlaps with active L2 table); further corruption events will be suppressed
 blkdebug: Suspended request '0'
 write failed: Input/output error
diff --git a/tests/qemu-iotests/289 b/tests/qemu-iotests/289
new file mode 100755
index 0000000000..13b4984721
--- /dev/null
+++ b/tests/qemu-iotests/289
@@ -0,0 +1,90 @@
+#!/usr/bin/env bash
+#
+# Test how 'qemu-io -c discard' behaves on v2 and v3 qcow2 images
+#
+# Copyright (C) 2020 Igalia, S.L.
+# Author: Alberto Garcia <berto@igalia.com>
+#
+# 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=berto@igalia.com
+
+seq=`basename $0`
+echo "QA output created by $seq"
+
+status=1    # failure is the default!
+
+_cleanup()
+{
+    _cleanup_test_img
+    rm -f "$TEST_IMG.backing"
+}
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+# get standard environment, filters and checks
+. ./common.rc
+. ./common.filter
+
+_supported_fmt qcow2
+_supported_proto file
+_supported_os Linux
+
+echo
+echo "### Test 'qemu-io -c discard' on a QCOW2 image without a backing file"
+echo
+for qcow2_compat in 0.10 1.1; do
+    echo "# Create an image with compat=$qcow2_compat without a backing file"
+    _make_test_img -o "compat=$qcow2_compat" 128k
+
+    echo "# Fill all clusters with data and then discard them"
+    $QEMU_IO -c 'write -P 0x01 0 128k' "$TEST_IMG" | _filter_qemu_io
+    $QEMU_IO -c 'discard 0 128k' "$TEST_IMG" | _filter_qemu_io
+
+    echo "# Read the data from the discarded clusters"
+    $QEMU_IO -c 'read -P 0x00 0 128k' "$TEST_IMG" | _filter_qemu_io
+done
+
+echo
+echo "### Test 'qemu-io -c discard' on a QCOW2 image with a backing file"
+echo
+
+echo "# Create a backing image and fill it with data"
+TEST_IMG="$TEST_IMG.backing" _make_test_img 128k
+$QEMU_IO -c 'write -P 0xff 0 128k' "$TEST_IMG.backing" | _filter_qemu_io
+
+for qcow2_compat in 0.10 1.1; do
+    echo "# Create an image with compat=$qcow2_compat and a backing file"
+    _make_test_img -o "compat=$qcow2_compat" -b "$TEST_IMG.backing"
+
+    echo "# Fill all clusters with data and then discard them"
+    $QEMU_IO -c 'write -P 0x01 0 128k' "$TEST_IMG" | _filter_qemu_io
+    $QEMU_IO -c 'discard 0 128k' "$TEST_IMG" | _filter_qemu_io
+
+    echo "# Read the data from the discarded clusters"
+    if [ "$qcow2_compat" = "1.1" ]; then
+        # In qcow2 v3 clusters are zeroed (with QCOW_OFLAG_ZERO)
+        $QEMU_IO -c 'read -P 0x00 0 128k' "$TEST_IMG" | _filter_qemu_io
+    else
+        # In qcow2 v2 if there's a backing image we cannot zero the clusters
+        # without exposing the backing file data so discard does nothing
+        $QEMU_IO -c 'read -P 0x01 0 128k' "$TEST_IMG" | _filter_qemu_io
+    fi
+done
+
+# success, all done
+echo "*** done"
+rm -f $seq.full
+status=0
diff --git a/tests/qemu-iotests/289.out b/tests/qemu-iotests/289.out
new file mode 100644
index 0000000000..dcd82c6d07
--- /dev/null
+++ b/tests/qemu-iotests/289.out
@@ -0,0 +1,52 @@
+QA output created by 289
+
+### Test 'qemu-io -c discard' on a QCOW2 image without a backing file
+
+# Create an image with compat=0.10 without a backing file
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=131072
+# Fill all clusters with data and then discard them
+wrote 131072/131072 bytes at offset 0
+128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+discard 131072/131072 bytes at offset 0
+128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+# Read the data from the discarded clusters
+read 131072/131072 bytes at offset 0
+128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+# Create an image with compat=1.1 without a backing file
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=131072
+# Fill all clusters with data and then discard them
+wrote 131072/131072 bytes at offset 0
+128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+discard 131072/131072 bytes at offset 0
+128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+# Read the data from the discarded clusters
+read 131072/131072 bytes at offset 0
+128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+### Test 'qemu-io -c discard' on a QCOW2 image with a backing file
+
+# Create a backing image and fill it with data
+Formatting 'TEST_DIR/t.IMGFMT.backing', fmt=IMGFMT size=131072
+wrote 131072/131072 bytes at offset 0
+128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+# Create an image with compat=0.10 and a backing file
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=131072 backing_file=TEST_DIR/t.IMGFMT.backing
+# Fill all clusters with data and then discard them
+wrote 131072/131072 bytes at offset 0
+128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+discard 131072/131072 bytes at offset 0
+128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+# Read the data from the discarded clusters
+read 131072/131072 bytes at offset 0
+128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+# Create an image with compat=1.1 and a backing file
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=131072 backing_file=TEST_DIR/t.IMGFMT.backing
+# Fill all clusters with data and then discard them
+wrote 131072/131072 bytes at offset 0
+128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+discard 131072/131072 bytes at offset 0
+128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+# Read the data from the discarded clusters
+read 131072/131072 bytes at offset 0
+128 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 ec2b2302e5..891b3ce858 100644
--- a/tests/qemu-iotests/group
+++ b/tests/qemu-iotests/group
@@ -295,3 +295,4 @@
 284 rw
 286 rw quick
 288 quick
+289 rw auto quick
