diff --git a/synapse/config/server.py b/synapse/config/server.py
index 8efab924d4..aa71835dc3 100644
--- a/synapse/config/server.py
+++ b/synapse/config/server.py
@@ -165,7 +165,7 @@ class ServerConfig(Config):
         # How long to keep redacted events in the database in unredacted form
         # before redacting them.
         redaction_retention_period = config.get("redaction_retention_period")
-        if redaction_retention_period:
+        if redaction_retention_period is not None:
             self.redaction_retention_period = self.parse_duration(
                 redaction_retention_period
             )
diff --git a/synapse/storage/events.py b/synapse/storage/events.py
index a5d13ddc49..77ba7eb2af 100644
--- a/synapse/storage/events.py
+++ b/synapse/storage/events.py
@@ -1566,7 +1566,7 @@ class EventsStore(
             Deferred
         """
 
-        if not self.hs.config.redaction_retention_period:
+        if self.hs.config.redaction_retention_period is None:
             return
 
         max_pos = yield self.find_first_stream_ordering_after_ts(