diff --git a/tests/qemu-iotests/037 b/tests/qemu-iotests/037
index 9171d8c8a6..586245159f 100755
--- a/tests/qemu-iotests/037
+++ b/tests/qemu-iotests/037
@@ -51,6 +51,9 @@ size=128M
 echo
 echo "== creating backing file for COW tests =="
 
+TEST_IMG_SAVE="$TEST_IMG"
+TEST_IMG="$TEST_IMG.base"
+
 _make_test_img $size
 
 function backing_io()
@@ -71,7 +74,7 @@ function backing_io()
 
 backing_io 0 256 write | $QEMU_IO "$TEST_IMG" | _filter_qemu_io
 
-mv "$TEST_IMG" "$TEST_IMG.base"
+TEST_IMG="$TEST_IMG_SAVE"
 
 _make_test_img -b "$TEST_IMG.base" 6G
 
diff --git a/tests/qemu-iotests/037.out b/tests/qemu-iotests/037.out
index 55b30fdc63..cd6710c901 100644
--- a/tests/qemu-iotests/037.out
+++ b/tests/qemu-iotests/037.out
@@ -1,7 +1,7 @@
 QA output created by 037
 
 == creating backing file for COW tests ==
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728
+Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134217728
 wrote 512/512 bytes at offset 0
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 wrote 512/512 bytes at offset 512