diff --git a/oauth2client/contrib/_metadata.py b/oauth2client/contrib/_metadata.py
index 564cd398..6f9f5033 100644
--- a/oauth2client/contrib/_metadata.py
+++ b/oauth2client/contrib/_metadata.py
@@ -29,8 +29,13 @@
 from oauth2client import transport
 
 
+
+_GCE_METADATA_HOST = os.getenv('GCE_METADATA_HOST', os.getenv(
+        'GCE_METADATA_ROOT', "metadata.google.internal"
+    ))
+
 METADATA_ROOT = 'http://{}/computeMetadata/v1/'.format(
-    os.getenv('GCE_METADATA_ROOT', 'metadata.google.internal'))
+    _GCE_METADATA_HOST)
 METADATA_HEADERS = {'Metadata-Flavor': 'Google'}