diff --git a/websocket-sharp/Server/WebSocketSessionManager.cs b/websocket-sharp/Server/WebSocketSessionManager.cs
index a0fa6cce..08e2e682 100644
--- a/websocket-sharp/Server/WebSocketSessionManager.cs
+++ b/websocket-sharp/Server/WebSocketSessionManager.cs
@@ -759,7 +759,7 @@ namespace WebSocketSharp.Server
     ///   <para>
     ///   It represents a collection of pairs of a session ID and
     ///   a value indicating whether a pong has been received from
-    ///   its client within a time.
+    ///   the client within a time.
     ///   </para>
     /// </returns>
     /// <exception cref="InvalidOperationException">