diff --git a/substrate/frame/im-online/src/lib.rs b/substrate/frame/im-online/src/lib.rs
index e280a89054..7815db7072 100644
--- a/substrate/frame/im-online/src/lib.rs
+++ b/substrate/frame/im-online/src/lib.rs
@@ -264,7 +264,7 @@ decl_event!(
 		HeartbeatReceived(AuthorityId),
 		/// At the end of the session, no offence was committed.
 		AllGood,
-		/// At the end of the session, at least once validator was found to be offline.
+		/// At the end of the session, at least one validator was found to be offline.
 		SomeOffline(Vec<IdentificationTuple>),
 	}
 );