diff --git a/lib/server/session.js b/lib/server/session.js
index 0a07814a..d2863082 100644
--- a/lib/server/session.js
+++ b/lib/server/session.js
@@ -65,9 +65,6 @@ function Session(instance, stream) {
   // map of collection name -> {doc name: stream || true || false}
   this.collections = {};
 
-  // Map from cName -> docName -> version the client has.
-  this.knownVersions = {};
-
   // Map from query ID -> emitter.
   this.queries = {};
 
@@ -145,13 +142,6 @@ Session.prototype._setSubscribed = function(c, docName, value, v) {
   }
   // Set to new value
   docs[docName] = value;
-
-  var vs = (this.knownVersions[c] || (this.knownVersions[c] = {}));
-  if (typeof v === 'number') {
-    vs[docName] = v;
-  } else if (!value) {
-    delete vs[docName];
-  }
 };
 
 // Check whether or not the document is subscribed by this session.
@@ -503,17 +493,6 @@ Session.prototype._processQueryResults = function(collection, results, qopts) {
   return messages;
 };
 
-Session.prototype._mergeKnownVersions = function(collectionVersions) {
-  if (!collectionVersions) return;
-
-  for (var c in collectionVersions) {
-    for (var docName in collectionVersions[c]) {
-      var vs = (this.knownVersions[c] || (this.knownVersions[c] = {}));
-      vs[docName] = collectionVersions[c][docName];
-    }
-  }
-}
-
 // Handle an incoming message from the client. This is the actual guts of session.js.
 Session.prototype._handleMessage = function(req, callback) {
   // First some checks of the incoming request. Error will be set to a value if a problem is found.
@@ -542,9 +521,8 @@ Session.prototype._handleMessage = function(req, callback) {
       if (qopts.docMode != null && qopts.docMode !== 'fetch' && qopts.docMode !== 'sub')
         return callback('invalid query docmode: ' + qopts.docMode);
 
-      // Fill in known query data a previous session. Ignored if docMode isn't defined.
-      this._mergeKnownVersions(req.o.vs);
-      qopts.versions = this.knownVersions;
+      // The client tells us what versions it already has
+      qopts.versions = req.o.vs;
 
       // Enables polling mode, which forces the query to be rerun on the whole
       // index, not just the edited document.
diff --git a/package.json b/package.json
index 0cb63572..3058a9f6 100644
--- a/package.json
+++ b/package.json
@@ -26,7 +26,11 @@
     "optimist": ">= 0.2.4",
     "browserchannel": "*",
     "mocha": "~1",
-    "uglify-js": "~2"
+    "chai": "*",
+    "sinon": "^1.12.2",
+    "uglify-js": "~2",
+    "sinon": "^1.4.0",
+    "connect": "^3.3.0"
   },
   "optionalDependencies": {
     "express": "~3"
diff --git a/test/server/useragent.coffee b/test/server/useragent.coffee
index 013e6cd3..93cfce2f 100644
--- a/test/server/useragent.coffee
+++ b/test/server/useragent.coffee
@@ -2,6 +2,7 @@ UserAgent = require '../../lib/server/useragent'
 {Readable} = require 'stream'
 {EventEmitter} = require 'events'
 assert = require 'assert'
+sinon = require 'sinon'
 
 describe 'UserAgent', ->