diff --git a/cms/djangoapps/api/v1/serializers/course_runs.py b/cms/djangoapps/api/v1/serializers/course_runs.py
index 10737564ef..90de622bac 100644
--- a/cms/djangoapps/api/v1/serializers/course_runs.py
+++ b/cms/djangoapps/api/v1/serializers/course_runs.py
@@ -8,6 +8,7 @@ import six
 from django.contrib.auth import get_user_model
 from django.db import transaction
 from django.utils.translation import ugettext_lazy as _
+from opaque_keys import InvalidKeyError
 from rest_framework import serializers
 from rest_framework.fields import empty
 
@@ -168,29 +169,40 @@ class CourseRunCreateSerializer(CourseRunSerializer):
 class CourseRunRerunSerializer(CourseRunSerializerCommonFieldsMixin, CourseRunTeamSerializerMixin,
                                serializers.Serializer):
     title = serializers.CharField(source='display_name', required=False)
+    number = serializers.CharField(source='id.course', required=False)
     run = serializers.CharField(source='id.run')
 
-    def validate_run(self, value):
+    def validate(self, attrs):
         course_run_key = self.instance.id
+        _id = attrs.get('id')
+        number = _id.get('course', course_run_key.course)
+        run = _id['run']
         store = modulestore()
-        with store.default_store('split'):
-            new_course_run_key = store.make_course_key(course_run_key.org, course_run_key.course, value)
+        try:
+            with store.default_store('split'):
+                new_course_run_key = store.make_course_key(course_run_key.org, number, run)
+        except InvalidKeyError:
+            raise serializers.ValidationError(
+                u'Invalid key supplied. Ensure there are no special characters in the Course Number.'
+            )
         if store.has_course(new_course_run_key, ignore_case=True):
-            raise serializers.ValidationError(u'Course run {key} already exists'.format(key=new_course_run_key))
-        return value
+            raise serializers.ValidationError(
+                {'run': u'Course run {key} already exists'.format(key=new_course_run_key)}
+            )
+        return attrs
 
     def update(self, instance, validated_data):
         course_run_key = instance.id
         _id = validated_data.pop('id')
+        number = _id.get('course', course_run_key.course)
+        run = _id['run']
         team = validated_data.pop('team', [])
         user = self.context['request'].user
         fields = {
             'display_name': instance.display_name
         }
         fields.update(validated_data)
-        new_course_run_key = rerun_course(
-            user, course_run_key, course_run_key.org, course_run_key.course, _id['run'], fields, False
-        )
+        new_course_run_key = rerun_course(user, course_run_key, course_run_key.org, number, run, fields, False)
 
         course_run = get_course_and_check_access(new_course_run_key, user)
         self.update_team(course_run, team)
diff --git a/cms/djangoapps/api/v1/tests/test_views/test_course_runs.py b/cms/djangoapps/api/v1/tests/test_views/test_course_runs.py
index 8ce1b997d1..cdc1d3819d 100644
--- a/cms/djangoapps/api/v1/tests/test_views/test_course_runs.py
+++ b/cms/djangoapps/api/v1/tests/test_views/test_course_runs.py
@@ -321,18 +321,18 @@ class CourseRunViewSetTests(ModuleStoreTestCase):
         contentstore().find(content_key)
 
     @ddt.data(
-        ('instructor_paced', False),
-        ('self_paced', True),
+        ('instructor_paced', False, 'NotOriginalNumber1x'),
+        ('self_paced', True, None),
     )
     @ddt.unpack
-    def test_rerun(self, pacing_type, expected_self_paced_value):
-        course_run = ToyCourseFactory()
+    def test_rerun(self, pacing_type, expected_self_paced_value, number):
+        original_course_run = ToyCourseFactory()
         start = datetime.datetime.now(pytz.UTC).replace(microsecond=0)
         end = start + datetime.timedelta(days=30)
         user = UserFactory()
         role = 'instructor'
         run = '3T2017'
-        url = reverse('api:v1:course_run-rerun', kwargs={'pk': str(course_run.id)})
+        url = reverse('api:v1:course_run-rerun', kwargs={'pk': str(original_course_run.id)})
         data = {
             'run': run,
             'schedule': {
@@ -347,13 +347,25 @@ class CourseRunViewSetTests(ModuleStoreTestCase):
             ],
             'pacing_type': pacing_type,
         }
+        # If number is supplied, this should become the course number used in the course run key
+        # If not, it should default to the original course run number that the rerun is based on.
+        if number:
+            data.update({'number': number})
         response = self.client.post(url, data, format='json')
         assert response.status_code == 201
 
         course_run_key = CourseKey.from_string(response.data['id'])
         course_run = modulestore().get_course(course_run_key)
+
         assert course_run.id.run == run
         assert course_run.self_paced is expected_self_paced_value
+
+        if number:
+            assert course_run.id.course == number
+            assert course_run.id.course != original_course_run.id.course
+        else:
+            assert course_run.id.course == original_course_run.id.course
+
         self.assert_course_run_schedule(course_run, start, end)
         self.assert_access_role(course_run, user, role)
         self.assert_course_access_role_count(course_run, 1)
@@ -367,3 +379,16 @@ class CourseRunViewSetTests(ModuleStoreTestCase):
         response = self.client.post(url, data, format='json')
         assert response.status_code == 400
         assert response.data == {'run': [u'Course run {key} already exists'.format(key=course_run.id)]}
+
+    def test_rerun_invalid_number(self):
+        course_run = ToyCourseFactory()
+        url = reverse('api:v1:course_run-rerun', kwargs={'pk': str(course_run.id)})
+        data = {
+            'run': '2T2019',
+            'number': '!@#$%^&*()',
+        }
+        response = self.client.post(url, data, format='json')
+        assert response.status_code == 400
+        assert response.data == {'non_field_errors': [
+            u'Invalid key supplied. Ensure there are no special characters in the Course Number.'
+        ]}