diff --git a/server/assignments/schema/mutations.py b/server/assignments/schema/mutations.py
index 0a3951fa..7bb4c23d 100644
--- a/server/assignments/schema/mutations.py
+++ b/server/assignments/schema/mutations.py
@@ -1,4 +1,5 @@
 import graphene
+from django.core.exceptions import MultipleObjectsReturned
 from graphene import relay
 from graphql_relay import from_global_id
 from rest_framework.exceptions import PermissionDenied
@@ -22,7 +23,13 @@ class UpdateAssignment(relay.ClientIDMutation):
     def mutate_and_get_payload(cls, root, info, **kwargs):
         assignment_data = kwargs.get('assignment')
         assignment = get_object(Assignment, assignment_data.get('id'))
-        (submission, created) = assignment.submissions.get_or_create(student=info.context.user)
+
+        try:
+            (submission, _created) = assignment.submissions.get_or_create(student=info.context.user)
+        except MultipleObjectsReturned:
+            for submission in assignment.submissions.filter(student=info.context.user):
+                submission.delete()
+            submission = assignment.submissions.create(student=info.context.user)
         submission.text = assignment_data.get('answer', '')
         submission.document = assignment_data.get('document', '')
         final = assignment_data.get('final')
diff --git a/server/assignments/tests/test_duplicate_student_submissions.py b/server/assignments/tests/test_duplicate_student_submissions.py
new file mode 100644
index 00000000..6c8d8667
--- /dev/null
+++ b/server/assignments/tests/test_duplicate_student_submissions.py
@@ -0,0 +1,60 @@
+from django.test import TestCase, RequestFactory
+from graphene.test import Client
+from graphql_relay import to_global_id
+
+from api.schema import schema
+from assignments.factories import AssignmentFactory
+from assignments.models import StudentSubmission
+from users.models import User
+from users.services import create_users
+
+UPDATE_ASSIGNMENT_MUTATION = """
+mutation UpdateAssignment($input: UpdateAssignmentInput!) {
+  updateAssignment(input: $input) {
+    updatedAssignment {      
+      id
+      submission {
+        id
+        text
+        final
+      }
+    }
+  }
+}
+"""
+
+
+class DuplicateStudentSubmissionsTestCase(TestCase):
+    def setUp(self):
+        create_users()
+
+        self.student1 = User.objects.get(username='student1')
+        self.assignment = AssignmentFactory()
+        self.assignment_id = to_global_id('AssignmentNode', self.assignment.id)
+
+        # create 2 submissions, can happen if multiple requests arrive simultaneously
+        StudentSubmission.objects.create(assignment=self.assignment, student=self.student1, text='abc')
+        StudentSubmission.objects.create(assignment=self.assignment, student=self.student1, text='abcd')
+
+        request = RequestFactory().get('/')
+        request.user = self.student1
+        self.client = Client(schema=schema, context_value=request)
+
+    def test_returns_one_submission(self):
+        query = UPDATE_ASSIGNMENT_MUTATION
+        answer = "Abcdefg"
+        variables = {
+            "input": {
+                "assignment": {
+                    "answer": answer,
+                    "document": "",
+                    "final": True,
+                    "id": self.assignment_id
+                }
+            }
+        }
+
+        result = self.client.execute(query, variables=variables)
+        self.assertIsNone(result.get('errors'))
+        self.assertEquals(
+            result.get('data').get('updateAssignment').get('updatedAssignment').get('submission').get('text'), answer)
diff --git a/server/core/settings.py b/server/core/settings.py
index ddcfd7ee..7ed5597c 100644
--- a/server/core/settings.py
+++ b/server/core/settings.py
@@ -328,20 +328,14 @@ if not DEBUG and os.environ.get('SENTRY_DSN'):
         event['user'] = {'id': id}
         return event
 
+    environment = os.environ.get('SENTRY_ENV', 'localhost')
+
     sentry_sdk.init(
         dsn=os.environ.get('SENTRY_DSN'),
         integrations=[DjangoIntegration()],
         send_default_pii=True,
-        before_send=before_send
-    )
-
-if not DEBUG and os.environ.get('SENTRY_DSN'):
-    import sentry_sdk
-    from sentry_sdk.integrations.django import DjangoIntegration
-
-    sentry_sdk.init(
-        dsn=os.environ.get('SENTRY_DSN'),
-        integrations=[DjangoIntegration()]
+        before_send=before_send,
+        environment=environment
     )
 
     # LOGGING['handlers'] = {
diff --git a/server/notes/tests.py b/server/notes/tests.py
deleted file mode 100644
index 7ce503c2..00000000
--- a/server/notes/tests.py
+++ /dev/null
@@ -1,3 +0,0 @@
-from django.test import TestCase
-
-# Create your tests here.