diff --git a/synapse/events/validator.py b/synapse/events/validator.py
index 6c65ce810..63bbc9059 100644
--- a/synapse/events/validator.py
+++ b/synapse/events/validator.py
@@ -64,6 +64,8 @@ class EventValidator:
             # Note that only the client controlled portion of the event is
             # checked, since we trust the portions of the event we created.
             validate_canonicaljson(event.content)
+        if not 0 < event.origin_server_ts < 2 ** 53:
+            raise SynapseError(400, "Event timestamp is out of range")
 
         # meow: allow specific users to send potentially dangerous events.
         if event.sender in config.meow.validation_override: