2 files changed, 5 insertions, 1 deletions
diff --git a/changelog.d/4164.bugfix b/changelog.d/4164.bugfix
new file mode 100644
index 0000000000..f70e0b2056
--- /dev/null
+++ b/changelog.d/4164.bugfix
@@ -0,0 +1 @@
+Fix noop checks when updating device keys, reducing spurious device list update notifications.
diff --git a/synapse/storage/end_to_end_keys.py b/synapse/storage/end_to_end_keys.py
index 1f1721e820..2a0f6cfca9 100644
--- a/synapse/storage/end_to_end_keys.py
+++ b/synapse/storage/end_to_end_keys.py
@@ -40,7 +40,10 @@ class EndToEndKeyStore(SQLBaseStore):
                 allow_none=True,
             )
 
-            new_key_json = encode_canonical_json(device_keys)
+            # In py3 we need old_key_json to match new_key_json type. The DB
+            # returns unicode while encode_canonical_json returns bytes.
+            new_key_json = encode_canonical_json(device_keys).decode("utf-8")
+
             if old_key_json == new_key_json:
                 return False