diff --git a/src/Room.c b/src/Room.c
index 652c083..c17499a 100644
--- a/src/Room.c
+++ b/src/Room.c
@@ -499,6 +499,9 @@ PopulateEventV1(Room * room, HashMap * event, PduV1 * pdu, ServerPart serv)
     pdu->room_id = StrDuplicate(room->id);
     pdu->signatures = HashMapCreate();
     pdu->depth = RoomGetDepth(room) + 1; /* TODO: Clamp this value. */
+    pdu->depth = 
+        pdu->depth >= (int64_t) UINT64_MAX ? 
+            (int64_t) UINT64_MAX : pdu->depth;
 
     /* Create a random event ID for this PDU.
      * TODO: Optionally verify whenever it's already used, but that