diff --git a/tests/qemu-iotests/tests/backup-discard-source b/tests/qemu-iotests/tests/backup-discard-source
index 2391b12..05fbe5d 100755
--- a/tests/qemu-iotests/tests/backup-discard-source
+++ b/tests/qemu-iotests/tests/backup-discard-source
@@ -28,7 +28,7 @@
 temp_img = os.path.join(iotests.test_dir, 'temp')
 source_img = os.path.join(iotests.test_dir, 'source')
 target_img = os.path.join(iotests.test_dir, 'target')
-size = '1M'
+size = 1024 * 1024
 
 
 def get_actual_size(vm, node_name):
@@ -39,9 +39,9 @@
 
 class TestBackup(iotests.QMPTestCase):
     def setUp(self):
-        qemu_img_create('-f', iotests.imgfmt, source_img, size)
-        qemu_img_create('-f', iotests.imgfmt, temp_img, size)
-        qemu_img_create('-f', iotests.imgfmt, target_img, size)
+        qemu_img_create('-f', iotests.imgfmt, source_img, str(size))
+        qemu_img_create('-f', iotests.imgfmt, temp_img, str(size))
+        qemu_img_create('-f', iotests.imgfmt, target_img, str(size))
         qemu_io('-c', 'write 0 1M', source_img)
 
         self.vm = iotests.VM()
@@ -98,7 +98,7 @@
         mapping = qemu_img_map(temp_img)
         self.assertEqual(len(mapping), 1)
         self.assertEqual(mapping[0]['start'], 0)
-        self.assertEqual(mapping[0]['length'], 1024 * 1024)
+        self.assertEqual(mapping[0]['length'], size)
         self.assertEqual(mapping[0]['data'], False)
 
         os.remove(temp_img)
@@ -125,7 +125,7 @@
         self.assert_qmp(result, 'return', '')
 
         # Check that data is written to temporary image
-        self.assertGreater(get_actual_size(self.vm, 'temp'), 1024 * 1024)
+        self.assertGreater(get_actual_size(self.vm, 'temp'), size)
 
         self.do_backup()