diff --git a/paunch/builder/base.py b/paunch/builder/base.py
index f9fee2a..e119c3b 100644
--- a/paunch/builder/base.py
+++ b/paunch/builder/base.py
@@ -212,7 +212,9 @@ class BaseBuilder(object):
         for image in sorted(images):
 
             # only pull if the image does not exist locally
-            if self.runner.inspect(image, format='exists', type='image'):
+            if self.runner.inspect(image,
+                                   output_format='exists',
+                                   o_type='image'):
                 continue
 
             try:
diff --git a/paunch/runner.py b/paunch/runner.py
index 14abbf8..108d49d 100644
--- a/paunch/runner.py
+++ b/paunch/runner.py
@@ -73,17 +73,17 @@ class BaseRunner(object):
 
         return [c for c in cmd_stdout.split()]
 
-    def inspect(self, name, format=None, type='container'):
-        cmd = [self.cont_cmd, 'inspect', '--type', type]
-        if format:
+    def inspect(self, name, output_format=None, o_type='container'):
+        cmd = [self.cont_cmd, 'inspect', '--type', o_type]
+        if output_format:
             cmd.append('--format')
-            cmd.append(format)
+            cmd.append(output_format)
         cmd.append(name)
         (cmd_stdout, cmd_stderr, returncode) = self.execute(cmd, self.log)
         if returncode != 0:
             return
         try:
-            if format:
+            if output_format:
                 return cmd_stdout
             else:
                 return json.loads(cmd_stdout)[0]
@@ -93,7 +93,7 @@ class BaseRunner(object):
 
     def unique_container_name(self, container):
         container_name = container
-        while self.inspect(container_name, format='exists'):
+        while self.inspect(container_name, output_format='exists'):
             suffix = ''.join(random.choice(
                 string.ascii_lowercase + string.digits) for i in range(8))
             container_name = '%s-%s' % (container, suffix)
diff --git a/paunch/tests/test_runner.py b/paunch/tests/test_runner.py
index 0a71e16..51c4435 100644
--- a/paunch/tests/test_runner.py
+++ b/paunch/tests/test_runner.py
@@ -90,7 +90,7 @@ class TestBaseRunner(base.TestCase):
 
         self.assertEqual(
             "bar",
-            self.runner.inspect('one', format='{{foo}}')
+            self.runner.inspect('one', output_format='{{foo}}')
         )
         self.assert_execute(
             popen, ['docker', 'inspect', '--type', 'container',