diff --git a/websocket-sharp/Mask.cs b/websocket-sharp/Mask.cs
index 018751d2..5e308398 100644
--- a/websocket-sharp/Mask.cs
+++ b/websocket-sharp/Mask.cs
@@ -42,10 +42,10 @@ namespace WebSocketSharp
     /// <summary>
     /// Equivalent to numeric value 0. Indicates not masked.
     /// </summary>
-    Unmask = 0x0,
+    None = 0x0,
     /// <summary>
     /// Equivalent to numeric value 1. Indicates masked.
     /// </summary>
-    Mask = 0x1
+    Masked = 0x1
   }
 }
diff --git a/websocket-sharp/WebSocketFrame.cs b/websocket-sharp/WebSocketFrame.cs
index 5ff0b833..fbd78a8b 100644
--- a/websocket-sharp/WebSocketFrame.cs
+++ b/websocket-sharp/WebSocketFrame.cs
@@ -124,12 +124,12 @@ namespace WebSocketSharp
       }
 
       if (mask) {
-        _mask = Mask.Mask;
+        _mask = Mask.Masked;
         _maskingKey = createMaskingKey ();
         payloadData.Mask (_maskingKey);
       }
       else {
-        _mask = Mask.Unmask;
+        _mask = Mask.None;
         _maskingKey = WebSocket.EmptyBytes;
       }
 
@@ -222,7 +222,7 @@ namespace WebSocketSharp
 
     public bool IsMasked {
       get {
-        return _mask == Mask.Mask;
+        return _mask == Mask.Masked;
       }
     }
 
@@ -456,7 +456,7 @@ Extended Payload Length: {7}
       var opcode = (Opcode) (header[0] & 0x0f);
 
       // MASK
-      var mask = (header[1] & 0x80) == 0x80 ? Mask.Mask : Mask.Unmask;
+      var mask = (header[1] & 0x80) == 0x80 ? Mask.Masked : Mask.None;
 
       // Payload Length
       var payloadLen = (byte) (header[1] & 0x7f);
@@ -712,10 +712,10 @@ Extended Payload Length: {7}
 
     internal void Unmask ()
     {
-      if (_mask == Mask.Unmask)
+      if (_mask == Mask.None)
         return;
 
-      _mask = Mask.Unmask;
+      _mask = Mask.None;
       _payloadData.Mask (_maskingKey);
       _maskingKey = WebSocket.EmptyBytes;
     }
@@ -755,7 +755,7 @@ Extended Payload Length: {7}
         if (_payloadLength > 125)
           buff.Write (_extPayloadLength, 0, _payloadLength == 126 ? 2 : 8);
 
-        if (_mask == Mask.Mask)
+        if (_mask == Mask.Masked)
           buff.Write (_maskingKey, 0, 4);
 
         if (_payloadLength > 0) {