diff --git a/websocket-sharp/Ext.cs b/websocket-sharp/Ext.cs
index 91983f89..42f50de6 100644
--- a/websocket-sharp/Ext.cs
+++ b/websocket-sharp/Ext.cs
@@ -508,6 +508,16 @@ namespace WebSocketSharp
       return value.StartsWith (method.ToExtensionString ());
     }
 
+    internal static bool IsControl (this byte opcode)
+    {
+      return opcode > 0x7 && opcode < 0x10;
+    }
+
+    internal static bool IsData (this byte opcode)
+    {
+      return opcode == 0x1 || opcode == 0x2;
+    }
+
     internal static bool IsPortNumber (this int value)
     {
       return value > 0 && value < 65536;
@@ -529,6 +539,11 @@ namespace WebSocketSharp
              code == CloseStatusCode.TlsHandshakeFailure;
     }
 
+    internal static bool IsSupported (this byte opcode)
+    {
+      return Enum.IsDefined (typeof (Opcode), opcode);
+    }
+
     internal static bool IsText (this string value)
     {
       var len = value.Length;
diff --git a/websocket-sharp/WebSocketFrame.cs b/websocket-sharp/WebSocketFrame.cs
index bf247a10..c81720fd 100644
--- a/websocket-sharp/WebSocketFrame.cs
+++ b/websocket-sharp/WebSocketFrame.cs
@@ -377,33 +377,16 @@ namespace WebSocketSharp
       return output.ToString ();
     }
 
-    private static bool isControl (byte opcode)
-    {
-      return opcode == (byte) Opcode.Close ||
-             opcode == (byte) Opcode.Ping ||
-             opcode == (byte) Opcode.Pong;
-    }
-
     private static bool isControl (Opcode opcode)
     {
       return opcode == Opcode.Close || opcode == Opcode.Ping || opcode == Opcode.Pong;
     }
 
-    private static bool isData (byte opcode)
-    {
-      return opcode == (byte) Opcode.Text || opcode == (byte) Opcode.Binary;
-    }
-
     private static bool isData (Opcode opcode)
     {
       return opcode == Opcode.Text || opcode == Opcode.Binary;
     }
 
-    private static bool isSupported (byte opcode)
-    {
-      return Enum.IsDefined (typeof (Opcode), opcode);
-    }
-
     private static string print (WebSocketFrame frame)
     {
       // Payload Length
@@ -478,13 +461,13 @@ Extended Payload Length: {7}
       var payloadLen = (byte) (header[1] & 0x7f);
 
       // Check if valid header.
-      var err = !isSupported (opcode)
+      var err = !opcode.IsSupported ()
                 ? "An unsupported opcode."
-                : isControl (opcode) && fin == Fin.More
+                : opcode.IsControl () && fin == Fin.More
                   ? "A control frame is fragmented."
-                  : isControl (opcode) && payloadLen > 125
+                  : opcode.IsControl () && payloadLen > 125
                     ? "A control frame has a long payload length."
-                    : !isData (opcode) && rsv1 == Rsv.On
+                    : !opcode.IsData () && rsv1 == Rsv.On
                       ? "A non data frame is compressed."
                       : null;