diff --git a/common/djangoapps/student/models.py b/common/djangoapps/student/models.py
index da7ce8d4b1..6da10a300f 100644
--- a/common/djangoapps/student/models.py
+++ b/common/djangoapps/student/models.py
@@ -2269,9 +2269,11 @@ def get_user_by_username_or_email(username_or_email):
         retired, or the user is in the process of being retired.
     """
     username_or_email = strip_if_string(username_or_email)
+    user = None
     if '@' in username_or_email:
-        user = User.objects.get(email=username_or_email)
-    else:
+        user = User.objects.filter(email=username_or_email).first()
+
+    if user is None:
         user = User.objects.get(username=username_or_email)
         UserRetirementRequest = apps.get_model('user_api', 'UserRetirementRequest')
         if UserRetirementRequest.has_user_requested_retirement(user):
diff --git a/lms/djangoapps/instructor/tests/test_tools.py b/lms/djangoapps/instructor/tests/test_tools.py
index 7d05da99dd..22236e3266 100644
--- a/lms/djangoapps/instructor/tests/test_tools.py
+++ b/lms/djangoapps/instructor/tests/test_tools.py
@@ -8,6 +8,7 @@ import unittest
 
 import mock
 import six
+from django.contrib.auth.models import User
 from django.test import TestCase
 from django.test.utils import override_settings
 from pytz import UTC
@@ -357,3 +358,31 @@ def msk_from_problem_urlname(course_id, urlname, block_type='problem'):
         urlname = urlname[:-4]
 
     return course_id.make_usage_key(block_type, urlname)
+
+
+@attr(shard=1)
+class TestStudentFromIdentifier(TestCase):
+    """
+    Test get_student_from_identifier()
+    """
+    def setUp(self):
+        """
+        Fixtures
+        """
+        super(TestStudentFromIdentifier, self).setUp()
+        self.students = [
+            UserFactory.create(username='foo@touchstone'),  # a student with character `@` in user name
+            UserFactory.create()
+        ]
+
+    def test_valid_student_id(self):
+        for student in self.students:
+            assert student == tools.get_student_from_identifier(student.username)
+
+    def test_valid_student_email(self):
+        for student in self.students:
+            assert student == tools.get_student_from_identifier(student.email)
+
+    def test_invalid_student_id(self):
+        with self.assertRaises(User.DoesNotExist):
+            assert tools.get_student_from_identifier("invalid")