diff --git a/README.md b/README.md
index f7b4762..c9d9509 100644
--- a/README.md
+++ b/README.md
@@ -285,31 +285,8 @@ their use of RSV bits are not activated.
 #### *Session*
 
 The *Session* API must be implemented by both client and server sessions. It
-contains three methods: `validFrameRsv(frame)`,
-`processIncomingMessage(message)` and `processOutgoingMessage(message)`.
-
-```js
-session.validFrameRsv(frame)
-```
-
-This takes a *Frame* as defined above, and returns a response indicating which
-RSV bits are allowed to be set on the frame. (If a session is having this method
-called, the session is active and should its bits can be used.) For example, the
-`permessage-deflate` extension allows the RSV1 bit to be set on `text` and
-`binary` frames, and implements this method like this:
-
-```js
-Session.prototype.validFrameRsv = function(frame) {
-  if (frame.opcode === 1 || frame.opcode === 2) {
-    return {rsv1: true, rsv2: false, rsv3: false};
-  else
-    return {rsv1: false, rsv2: false, rsv3: false};
-};
-```
-
-Note that returning `false` for an `rsvX` field does not mean the session is
-forbidding its use; the framework assumes all RSV bits are banned unless a
-session indicates otherwise.
+contains two methods, `processIncomingMessage(message)` and
+`processOutgoingMessage(message)`.
 
 ```js
 session.processIncomingMessage(message, function(error, msg) { ... })
diff --git a/lib/websocket_extensions.js b/lib/websocket_extensions.js
index 8bf796b..771496d 100644
--- a/lib/websocket_extensions.js
+++ b/lib/websocket_extensions.js
@@ -12,6 +12,8 @@ var Extensions = function() {
   this._index    = {}
 };
 
+Extensions.MESSAGE_OPCODES = [1, 2];
+
 var instance = {
   add: function(ext) {
     if (typeof ext.name !== 'string') throw new TypeError('extension.name must be a string');
@@ -111,14 +113,17 @@ var instance = {
 
   validFrameRsv: function(frame) {
     var allowed = {rsv1: false, rsv2: false, rsv3: false},
-        policy;
+        ext;
 
-    for (var i = 0, n = this._sessions.length; i < n; i++) {
-      policy = this._sessions[i][1].validFrameRsv(frame);
-      allowed.rsv1 = allowed.rsv1 || policy.rsv1;
-      allowed.rsv2 = allowed.rsv2 || policy.rsv2;
-      allowed.rsv3 = allowed.rsv3 || policy.rsv3;
+    if (Extensions.MESSAGE_OPCODES.indexOf(frame.opcode) >= 0) {
+      for (var i = 0, n = this._sessions.length; i < n; i++) {
+        ext = this._sessions[i][0];
+        allowed.rsv1 = allowed.rsv1 || ext.rsv1;
+        allowed.rsv2 = allowed.rsv2 || ext.rsv2;
+        allowed.rsv3 = allowed.rsv3 || ext.rsv3;
+      }
     }
+
     return (allowed.rsv1 || !frame.rsv1) &&
            (allowed.rsv2 || !frame.rsv2) &&
            (allowed.rsv3 || !frame.rsv3);