diff --git a/workers/dockerfilebuild.py b/workers/dockerfilebuild.py
index a45d82b67..60b29a109 100644
--- a/workers/dockerfilebuild.py
+++ b/workers/dockerfilebuild.py
@@ -223,6 +223,13 @@ class DockerfileBuildContext(object):
         raise RuntimeError(message)
 
   def pull(self):
+    image_and_tag_tuple = self._parsed_dockerfile.get_image_and_tag()
+    if image_and_tag_tuple is None or image_and_tag_tuple[0] is None:
+      self._build_logger('Missing FROM command in Dockerfile', build_logs.ERROR)
+      raise JobException('Missing FROM command in Dockerfile')
+
+    image_and_tag = ':'.join(image_and_tag_tuple)
+
     # Login with the specified credentials (if any).
     if self._pull_credentials:
       logger.debug('Logging in with pull credentials: %s@%s',
@@ -238,13 +245,6 @@ class DockerfileBuildContext(object):
                            registry=self._pull_credentials['registry'], reauth=True)
 
     # Pull the image, in case it was updated since the last build
-    image_and_tag_tuple = self._parsed_dockerfile.get_image_and_tag()
-    if image_and_tag_tuple is None or image_and_tag_tuple[0] is None:
-      self._build_logger('Missing FROM command in Dockerfile', build_logs.ERROR)
-      raise JobException('Missing FROM command in Dockerfile')
-
-    image_and_tag = ':'.join(image_and_tag_tuple)
-
     self._build_logger('Pulling base image: %s' % image_and_tag, log_data = {
       'phasestep': 'pull',
       'repo_url': image_and_tag