diff --git a/auth/scopes.py b/auth/scopes.py
index 932541969..c71e5faa7 100644
--- a/auth/scopes.py
+++ b/auth/scopes.py
@@ -75,6 +75,9 @@ IMPLIED_SCOPES = {
 
 
 def scopes_from_scope_string(scopes):
+  if not scopes:
+    return {}
+    
   return {ALL_SCOPES.get(scope, None) for scope in scopes.split(',')}