diff --git a/tests/qemu-iotests/055 b/tests/qemu-iotests/055
index 82b9f5f47d..4175fff5e4 100755
--- a/tests/qemu-iotests/055
+++ b/tests/qemu-iotests/055
@@ -469,7 +469,8 @@ class TestDriveCompression(iotests.QMPTestCase):
         qemu_img('create', '-f', fmt, blockdev_target_img,
                  str(TestDriveCompression.image_len), *args)
         if attach_target:
-            self.vm.add_drive(blockdev_target_img, format=fmt, interface="none")
+            self.vm.add_drive(blockdev_target_img,
+                              img_format=fmt, interface="none")
 
         self.vm.launch()
 
diff --git a/tests/qemu-iotests/iotests.py b/tests/qemu-iotests/iotests.py
index 6f6363f3ec..aca7d50524 100644
--- a/tests/qemu-iotests/iotests.py
+++ b/tests/qemu-iotests/iotests.py
@@ -486,21 +486,21 @@ class VM(qtest.QEMUQtestMachine):
         self._args.append(opts)
         return self
 
-    def add_drive(self, path, opts='', interface='virtio', format=imgfmt):
+    def add_drive(self, path, opts='', interface='virtio', img_format=imgfmt):
         '''Add a virtio-blk drive to the VM'''
         options = ['if=%s' % interface,
                    'id=drive%d' % self._num_drives]
 
         if path is not None:
             options.append('file=%s' % path)
-            options.append('format=%s' % format)
+            options.append('format=%s' % img_format)
             options.append('cache=%s' % cachemode)
             options.append('aio=%s' % aiomode)
 
         if opts:
             options.append(opts)
 
-        if format == 'luks' and 'key-secret' not in opts:
+        if img_format == 'luks' and 'key-secret' not in opts:
             # default luks support
             if luks_default_secret_object not in self._args:
                 self.add_object(luks_default_secret_object)