diff --git a/packages/mongo/doc_fetcher.js b/packages/mongo/doc_fetcher.js
index 3d4740bf34..c7e20f8a41 100644
--- a/packages/mongo/doc_fetcher.js
+++ b/packages/mongo/doc_fetcher.js
@@ -1,3 +1,5 @@
+import { EventEmitter } from 'events';
+
 export class DocFetcher {
   constructor(mongoConnection) {
     this._mongoConnection = mongoConnection;
@@ -14,7 +16,7 @@ export class DocFetcher {
   //
   // You may assume that callback is never called synchronously (and in fact
   // OplogObserveDriver does so).
-  fetch(collectionName, id, op, callback) {
+  async fetch(collectionName, id, op) {
     const self = this;
 
     check(collectionName, String);
@@ -22,36 +24,48 @@ export class DocFetcher {
 
     // If there's already an in-progress fetch for this cache key, yield until
     // it's done and return whatever it returns.
-    if (self._callbacksForOp.has(op)) {
-      self._callbacksForOp.get(op).push(callback);
-      return;
+    // console.log(self._callbacksForOp, {op});
+    // if (self._callbacksForOp.has(op)) {
+    //   self._callbacksForOp.get(op).push(callback);
+    //   return callback;
+    // }
+    // self._callbacksForOp.set(op, [callback]);
+    const inProgress = self._callbacksForOp.has(op);
+    if (!inProgress) {
+      self._callbacksForOp.set(op, new EventEmitter());
     }
-
-    const callbacks = [callback];
-    self._callbacksForOp.set(op, callbacks);
-
-    Meteor._runAsync(async function () {
-      try {
-        var doc = await self._mongoConnection.findOne(
-          collectionName, {_id: id}) || null;
-        // Return doc to all relevant callbacks. Note that this array can
-        // continue to grow during callback excecution.
-        while (callbacks.length > 0) {
-          // Clone the document so that the various calls to fetch don't return
-          // objects that are intertwingled with each other. Clone before
-          // popping the future, so that if clone throws, the error gets passed
-          // to the next callback.
-          await callbacks.pop()(null, EJSON.clone(doc));
-        }
-      } catch (e) {
-        while (callbacks.length > 0) {
-          await callbacks.pop()(e);
-        }
-      } finally {
-        // XXX consider keeping the doc around for a period of time before
-        // removing from the cache
-        self._callbacksForOp.delete(op);
-      }
+    const emitter =  self._callbacksForOp.get(op);
+    const callback = new Promise((resolve, reject) => {
+      emitter.once('data', (data) => {
+        resolve(data);
+      });
+      emitter.once('error', reject);
     });
+    if (inProgress) {
+      return callback;
+    }
+    Meteor._runAsync(async function () {
+          try {
+            var doc = await self._mongoConnection.findOne(
+                collectionName, {_id: id}) || null;
+            // Return doc to all relevant callbacks. Note that this array can
+            // continue to grow during callback excecution.
+            const evEmmiter = self._callbacksForOp.get(op);
+            if (evEmmiter) {
+              evEmmiter.emit('data', doc);
+            }
+          } catch (e) {
+            const evEmmiter = self._callbacksForOp.get(op);
+            if (evEmmiter) {
+              evEmmiter.emit('error', e);
+            }
+          } finally {
+            // XXX consider keeping the doc around for a period of time before
+            // removing from the cache
+            self._callbacksForOp.delete(op);
+          }
+        }
+    );
+    return callback;
   }
 }
diff --git a/packages/mongo/doc_fetcher_tests.js b/packages/mongo/doc_fetcher_tests.js
index 40cb214884..1ad4cbcff9 100644
--- a/packages/mongo/doc_fetcher_tests.js
+++ b/packages/mongo/doc_fetcher_tests.js
@@ -2,7 +2,6 @@ import { DocFetcher } from "./doc_fetcher.js";
 
 testAsyncMulti("mongo-livedata - doc fetcher", [
   async function (test, expect) {
-    var self = this;
     var collName = "docfetcher-" + Random.id();
     var collection = new Mongo.Collection(collName);
     var id1 = await collection.insert({x: 1});
@@ -14,26 +13,27 @@ testAsyncMulti("mongo-livedata - doc fetcher", [
     // Test basic operation.
     const fakeOp1 = {};
     const fakeOp2 = {};
-    // fetcher.fetch(collName, id1, fakeOp1, expect(null, {_id: id1, x: 1}));
-    // fetcher.fetch(collName, "nonexistent!", fakeOp2, expect(null, null));
-    //
-    // var fetched = false;
-    // var fakeOp3 = {};
-    // var expected = {_id: id2, y: 2};
-    // fetcher.fetch(collName, id2, fakeOp3, expect(function (e, d) {
-    //   fetched = true;
-    //   test.isFalse(e);
-    //   test.equal(d, expected);
-    // }));
-    // // The fetcher yields.
-    // test.isFalse(fetched);
-    //
-    // // Now ask for another document with the same op reference. Because a
-    // // fetch for that op is in flight, we will get the other fetch's
-    // // document, not this random document.
-    // fetcher.fetch(collName, Random.id(), fakeOp3, expect(function (e, d) {
-    //   test.isFalse(e);
-    //   test.equal(d, expected);
-    // }));
+    const promise1 = await fetcher.fetch(collName, id1, fakeOp1).then(expect({_id: id1, x: 1}));
+    const promise2 = fetcher.fetch(collName, "nonexistent!", fakeOp2).then(expect(null));
+
+    var fetched = false;
+    var fakeOp3 = {};
+    var expected = {_id: id2, y: 2};
+    const promise3 = fetcher.fetch(collName, id2, fakeOp3).then(expect(function (d) {
+      fetched = true;
+      test.equal(d, expected);
+    })).catch(expect(function (e) {
+      test.isFalse(e);
+    }));
+    test.isFalse(fetched);
+    // Now ask for another document with the same op reference. Because a
+    // fetch for that op is in flight, we will get the other fetch's
+    // document, not this random document.
+    const promise4 = fetcher.fetch(collName, Random.id(), fakeOp3).then(expect(function (d) {
+      test.equal(d, expected);
+    })).catch(expect(function (e) {
+      test.isFalse(e);
+    }));
+    await Promise.all([promise1, promise2, promise3, promise4]);
   }
 ]);