diff --git a/image/appc/__init__.py b/image/appc/__init__.py
index 1cae7181f..851c4698c 100644
--- a/image/appc/__init__.py
+++ b/image/appc/__init__.py
@@ -172,7 +172,7 @@ class DockerV1ToACIManifestTranslator(object):
   def build_manifest(repo_image, tag, synthetic_image_id):
     """ Builds an ACI manifest of an existing repository image. """
     docker_layer_data = JSONPathDict(repo_image.compat_metadata)
-    config = docker_layer_data['config'] or {}
+    config = docker_layer_data['config'] or JSONPathDict({})
 
     namespace = repo_image.repository.namespace_name
     repo_name = repo_image.repository.name
@@ -192,7 +192,7 @@ class DockerV1ToACIManifestTranslator(object):
     hostname = hostname.split(':', 1)[0]
 
     # Calculate the environment variables.
-    docker_env_vars = config.get('Env', []) or []
+    docker_env_vars = config.get('Env') or []
     env_vars = []
     for var in docker_env_vars:
       pieces = var.split('=')
@@ -212,26 +212,26 @@ class DockerV1ToACIManifestTranslator(object):
         },
         {
           "name": "arch",
-          "value": docker_layer_data.get('architecture', 'amd64')
+          "value": docker_layer_data.get('architecture') or 'amd64'
         },
         {
           "name": "os",
-          "value": docker_layer_data.get('os', 'linux')
+          "value": docker_layer_data.get('os') or 'linux'
         }
       ],
       "app": {
         "exec": exec_path,
         # Below, `or 'root'` is required to replace empty string from Dockerfiles.
-        "user": config.get('User', '') or 'root',
-        "group": config.get('Group', '') or 'root',
+        "user": config.get('User') or 'root',
+        "group": config.get('Group') or 'root',
         "eventHandlers": [],
-        "workingDirectory": config.get('WorkingDir', '') or '/',
+        "workingDirectory": config.get('WorkingDir') or '/',
         "environment": [{"name": key, "value": value} for (key, value) in env_vars],
         "isolators": DockerV1ToACIManifestTranslator._build_isolators(config),
         "mountPoints": DockerV1ToACIManifestTranslator._build_volumes(config),
         "ports": DockerV1ToACIManifestTranslator._build_ports(config),
         "annotations": [
-          {"name": "created", "value": docker_layer_data.get('created', '')},
+          {"name": "created", "value": docker_layer_data.get('created') or ''},
           {"name": "homepage", "value": source_url},
           {"name": "quay.io/derived-image", "value": synthetic_image_id},
         ]