diff --git a/lib/mongo_client.js b/lib/mongo_client.js
index e334d57fe7..b2737e0d04 100644
--- a/lib/mongo_client.js
+++ b/lib/mongo_client.js
@@ -16,7 +16,6 @@ const shallowClone = require('./utils').shallowClone;
 const authenticate = require('./authenticate');
 const ServerSessionPool = require('mongodb-core').Sessions.ServerSessionPool;
 const executeOperation = require('./utils').executeOperation;
-const isPromiseLike = require('./utils').isPromiseLike;
 
 /**
  * @fileOverview The **MongoClient** class is a class that allows for making Connections to MongoDB.
@@ -519,7 +518,12 @@ MongoClient.prototype.withSession = function(options, operation) {
   if (typeof options === 'function') (operation = options), (options = undefined);
   const session = this.startSession(options);
 
-  const cleanupHandler = (err, result, opts) => {
+  let cleanupHandler = (err, result, opts) => {
+    // prevent multiple calls to cleanupHandler
+    cleanupHandler = () => {
+      throw new ReferenceError('cleanupHandler was called too many times');
+    };
+
     opts = Object.assign({ throw: true }, opts);
     session.endSession();
 
diff --git a/test/functional/sessions_tests.js b/test/functional/sessions_tests.js
index ccb6b2612c..8501c81ecf 100644
--- a/test/functional/sessions_tests.js
+++ b/test/functional/sessions_tests.js
@@ -93,54 +93,6 @@ describe('Sessions', function() {
           operation: (/* client */) => (/* session */) => {
             throw new Error('something went wrong!');
           }
-        },
-        {
-          description: 'should support operations that return promises with a callback',
-          operation: client => session => {
-            return client
-              .db('test')
-              .collection('foo')
-              .find({}, { session })
-              .toArray();
-          },
-          callback: resolve => (err, res) => {
-            expect(err).to.not.exist;
-            expect(res).to.exist;
-            resolve();
-          }
-        },
-        {
-          description: 'should support operations that return rejected promises and a callback',
-          operation: (/* client */) => (/* session */) => {
-            return Promise.reject(new Error('something awful'));
-          },
-          callback: resolve => (err, res) => {
-            expect(err).to.exist;
-            expect(res).to.not.exist;
-            resolve();
-          }
-        },
-        {
-          description: "should support operations that don't return promises with a callback",
-          operation: (/* client */) => (/* session */) => {
-            setTimeout(() => {});
-          },
-          callback: resolve => (err, res) => {
-            expect(err).to.exist;
-            expect(res).to.not.exist;
-            resolve();
-          }
-        },
-        {
-          description: 'should support operations that throw exceptions with a callback',
-          operation: (/* client */) => (/* session */) => {
-            throw new Error('something went wrong!');
-          },
-          callback: resolve => (err, res) => {
-            expect(err).to.exist;
-            expect(res).to.not.exist;
-            resolve();
-          }
         }
       ].forEach(testCase => {
         it(testCase.description, function() {