diff --git a/packages/mongo-livedata/mongo_driver.js b/packages/mongo-livedata/mongo_driver.js
index 3a9f2d7945..b749682988 100644
--- a/packages/mongo-livedata/mongo_driver.js
+++ b/packages/mongo-livedata/mongo_driver.js
@@ -1562,11 +1562,6 @@ var cursorSupportedByOplogTailing = function (cursorDescription) {
   // First, check the options.
   var options = cursorDescription.options;
 
-  // We don't yet implement field filtering for oplog tailing (just because it's
-  // not implemented, not because there's a deep problem with implementing it).
-  // XXX Implementing field filtering should be a priority.
-  if (options.fields) return false;
-
   // This option (which are mostly used for sorted cursors) require us to figure
   // out where a given document fits in an order to know if it's included or
   // not, and we don't track that information when doing oplog tailing.
diff --git a/packages/mongo-livedata/oplog.js b/packages/mongo-livedata/oplog.js
index 37e200b6da..07706cd1dd 100644
--- a/packages/mongo-livedata/oplog.js
+++ b/packages/mongo-livedata/oplog.js
@@ -31,13 +31,16 @@ MongoConnection.prototype._observeChangesWithOplog = function (
 
   var published = new IdMap;
   var selector = LocalCollection._compileSelector(cursorDescription.selector);
+  var projection = cursorDescription.options.fields ?
+    LocalCollection._compileProjection(cursorDescription.options.fields) :
+    EJSON.clone;
 
   var needToFetch = new IdMap;
   var currentlyFetching = new IdMap;
 
   var add = function (doc) {
     var id = doc._id;
-    var fields = EJSON.clone(doc);
+    var fields = projection(doc);
     delete fields._id;
     if (published.has(id))
       throw Error("tried to add something already published " + id);
@@ -52,8 +55,10 @@ MongoConnection.prototype._observeChangesWithOplog = function (
     callbacks.removed && callbacks.removed(id);
   };
 
-  // XXX mutates newDoc, that's weird
+  // XXX it doesn't mutate newDoc anymore since we apply projection function but
+  // be careful refactoring and moving out projection.
   var handleDoc = function (id, newDoc) {
+    newDoc = projection(newDoc);
     var matchesNow = newDoc && selector(newDoc);
     var matchedBefore = published.has(id);
     if (matchesNow && !matchedBefore) {