diff --git a/googleapiclient/_auth.py b/googleapiclient/_auth.py
index 89a8a02..044ed12 100644
--- a/googleapiclient/_auth.py
+++ b/googleapiclient/_auth.py
@@ -18,6 +18,7 @@
 
 try:
     import google.auth
+    import google.auth.credentials
     import google_auth_httplib2
     HAS_GOOGLE_AUTH = True
 except ImportError:  # pragma: NO COVER