diff --git a/synapse/util/frozenutils.py b/synapse/util/frozenutils.py
index 1874464c8..fcfb38b3b 100644
--- a/synapse/util/frozenutils.py
+++ b/synapse/util/frozenutils.py
@@ -15,8 +15,6 @@
 
 from frozendict import frozendict
 
-import json
-
 
 def freeze(o):
     if isinstance(o, dict) or isinstance(o, frozendict):