diff --git a/spec/ParseUser.spec.js b/spec/ParseUser.spec.js
index ab95768e83..af554bf01a 100644
--- a/spec/ParseUser.spec.js
+++ b/spec/ParseUser.spec.js
@@ -3432,6 +3432,60 @@ describe('Parse.User testing', () => {
     });
   });
 
+  it('allows login when providing email as username', (done) => {
+    const user = new Parse.User();
+    user.save({
+      username: 'yolo',
+      password: 'yolopass',
+      email: 'yo@lo.com'
+    }).then(() => {
+      return Parse.User.logIn('yo@lo.com', 'yolopass');
+    }).then((user) => {
+      expect(user.get('username')).toBe('yolo');
+    }).then(done).catch(done.fail);
+  });
+
+  it('handles properly when 2 users share username / email pairs', (done) => {
+    const user = new Parse.User({
+      username: 'yo@loname.com',
+      password: 'yolopass',
+      email: 'yo@lo.com'
+    });
+    const user2 = new Parse.User({
+      username: 'yo@lo.com',
+      email: 'yo@loname.com',
+      password: 'yolopass2' // different passwords
+    });
+
+    Parse.Object.saveAll([user, user2]).then(() => {
+      return Parse.User.logIn('yo@loname.com', 'yolopass');
+    }).then((user) => {
+      // the username takes precedence over the email,
+      // so we get the user with username as passed in
+      expect(user.get('username')).toBe('yo@loname.com');
+    }).then(done).catch(done.fail);
+  });
+
+  it('handles properly when 2 users share username / email pairs, counterpart', (done) => {
+    const user = new Parse.User({
+      username: 'yo@loname.com',
+      password: 'yolopass',
+      email: 'yo@lo.com'
+    });
+    const user2 = new Parse.User({
+      username: 'yo@lo.com',
+      email: 'yo@loname.com',
+      password: 'yolopass2' // different passwords
+    });
+
+    Parse.Object.saveAll([user, user2]).then(() => {
+      return Parse.User.logIn('yo@loname.com', 'yolopass2');
+    }).then(done.fail).catch((err) => {
+      expect(err.message).toEqual('Invalid username/password.');
+      done();
+    });
+  });
+
   it('fails to login when password is not provided', (done) => {
     const user = new Parse.User();
     user.save({
diff --git a/src/Routers/UsersRouter.js b/src/Routers/UsersRouter.js
index 0cdba7b1e0..86763d7eea 100644
--- a/src/Routers/UsersRouter.js
+++ b/src/Routers/UsersRouter.js
@@ -84,13 +84,26 @@ export class UsersRouter extends ClassesRouter {
 
     let user;
     let isValidPassword = false;
-    const query = Object.assign({}, username ? { username } : {}, email ? { email } : {});
+    let query;
+    if (email && username) {
+      query = { email, username };
+    } else if (email) {
+      query = { email };
+    } else {
+      query = { $or: [{ username } , { email: username }] };
+    }
     return req.config.database.find('_User', query)
       .then((results) => {
         if (!results.length) {
           throw new Parse.Error(Parse.Error.OBJECT_NOT_FOUND, 'Invalid username/password.');
         }
-        user = results[0];
+
+        if (results.length > 1) { // corner case where user1 has username == user2 email
+          req.config.loggerController.warn('There is a user which email is the same as another user\'s username, logging in based on username');
+          user = results.filter((user) =>  user.username === username)[0];
+        } else {
+          user = results[0];
+        }
 
         if (req.config.verifyUserEmails && req.config.preventLoginWithUnverifiedEmail && !user.emailVerified) {
           throw new Parse.Error(Parse.Error.EMAIL_NOT_FOUND, 'User email is not verified.');