diff --git a/synapse/config/server.py b/synapse/config/server.py
index 38f6ff9ed..3463d53d1 100644
--- a/synapse/config/server.py
+++ b/synapse/config/server.py
@@ -955,7 +955,7 @@ class ServerConfig(Config):
           #purge_jobs:
           #  - shortest_max_lifetime: 1d
           #    longest_max_lifetime: 3d
-          #    interval: 5m:
+          #    interval: 5m
           #  - shortest_max_lifetime: 3d
           #    longest_max_lifetime: 1y
           #    interval: 24h