1 files changed, 1 insertions, 1 deletions
diff --git a/synapse/push/push_rule_evaluator.py b/synapse/push/push_rule_evaluator.py
index dca018af95..2a2b4437dc 100644
--- a/synapse/push/push_rule_evaluator.py
+++ b/synapse/push/push_rule_evaluator.py
@@ -304,7 +304,7 @@ def _flatten_dict(d, prefix=[], result={}):
         if isinstance(value, basestring):
             result[".".join(prefix + [key])] = value.lower()
         elif hasattr(value, "items"):
-            _flatten_dict(value, prefix=(prefix+[key]), result=result)
+            _flatten_dict(value, prefix=(prefix + [key]), result=result)
 
     return result