diff --git a/tests/qemu-iotests/iotests.py b/tests/qemu-iotests/iotests.py
index 52fc77563c73eb4e2cf15685321cb3d38d6b36e1..cba91a99272b8ad38d178467dd158d8b08dedcfa 100644
--- a/tests/qemu-iotests/iotests.py
+++ b/tests/qemu-iotests/iotests.py
@@ -289,7 +289,7 @@ def filter_testfiles(msg):
 
 def filter_qmp_testfiles(qmsg):
     def _filter(key, value):
-        if key == 'filename' or key == 'backing-file':
+        if is_str(value):
             return filter_testfiles(value)
         return value
     return filter_qmp(qmsg, _filter)