diff --git a/backend/api/fixtures/realistic/realistic.yaml b/backend/api/fixtures/realistic/realistic.yaml
index 5c3fcaf3..f7664d29 100644
--- a/backend/api/fixtures/realistic/realistic.yaml
+++ b/backend/api/fixtures/realistic/realistic.yaml
@@ -33,7 +33,7 @@
     visible: true
     archived: false
     locked_groups: false
-    start_date: 2024-12-12T00:00:00Z
+    start_date: 2023-12-12T00:00:00Z
     deadline: 2025-01-01T00:00:00Z
     max_score: 100
     score_visible: false
@@ -134,9 +134,18 @@
     project: 0
     obligated_extensions:
       - 0
-    blocked_extensions: []
+    blocked_extensions:
+      - 1
 - model: api.structurecheck
   pk: 1
+  fields:
+    path: "verslag/"
+    project: 0
+    obligated_extensions:
+      - 3
+    blocked_extensions: []
+- model: api.structurecheck
+  pk: 2
   fields:
     path: src/
     project: 1
@@ -145,7 +154,7 @@
     blocked_extensions:
       - 2
 - model: api.structurecheck
-  pk: 2
+  pk: 3
   fields:
     path: verslag/
     project: 1
@@ -153,7 +162,7 @@
       - 3
     blocked_extensions: []
 - model: api.structurecheck
-  pk: 3
+  pk: 4
   fields:
     path: ""
     project: 3
diff --git a/backend/api/locale/en/LC_MESSAGES/django.po b/backend/api/locale/en/LC_MESSAGES/django.po
index 9015d015..c481af8c 100755
--- a/backend/api/locale/en/LC_MESSAGES/django.po
+++ b/backend/api/locale/en/LC_MESSAGES/django.po
@@ -8,7 +8,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: PACKAGE VERSION\n"
 "Report-Msgid-Bugs-To: \n"
-"POT-Creation-Date: 2024-05-15 19:49+0200\n"
+"POT-Creation-Date: 2024-05-20 12:24+0200\n"
 "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
 "Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
 "Language-Team: LANGUAGE <LL@li.org>\n"
@@ -188,39 +188,43 @@ msgstr "The student is already in the group."
 msgid "group.errors.not_present"
 msgstr "The student is currently not in the group."
 
-#: serializers/project_serializer.py:22
+#: serializers/project_serializer.py:23
 msgid "project.errors.invalid_instance"
 msgstr "Error while parsing the provided zip."
 
-#: serializers/project_serializer.py:81
+#: serializers/project_serializer.py:122
 msgid "project.errors.context"
 msgstr "The project is not supplied in the context."
 
-#: serializers/project_serializer.py:86
+#: serializers/project_serializer.py:127
 msgid "project.errors.start_date_in_past"
 msgstr "The start date of the project lies in the past."
 
-#: serializers/project_serializer.py:100
+#: serializers/project_serializer.py:141
 msgid "project.errors.deadline_before_start_date"
 msgstr "The deadline of the project lies before the start date of the project."
 
-#: serializers/project_serializer.py:142
+#: serializers/project_serializer.py:183
 msgid "project.errors.zip_structure"
 msgstr "Error while parsing the provided zip."
 
-#: serializers/submission_serializer.py:96 tests/test_submission.py:275
+#: serializers/submission_serializer.py:98
+msgid "project.error.submissions.project_not_started"
+msgstr "The project hasn't started yet."
+
+#: serializers/submission_serializer.py:102 tests/test_submission.py:275
 msgid "project.error.submissions.past_project"
 msgstr "The deadline of the project has already passed."
 
-#: serializers/submission_serializer.py:99 tests/test_submission.py:346
+#: serializers/submission_serializer.py:105 tests/test_submission.py:346
 msgid "project.error.submissions.non_visible_project"
 msgstr "The project is currently in a non-visible state."
 
-#: serializers/submission_serializer.py:102 tests/test_submission.py:376
+#: serializers/submission_serializer.py:108 tests/test_submission.py:376
 msgid "project.error.submissions.archived_project"
 msgstr "The project is archived."
 
-#: serializers/submission_serializer.py:105
+#: serializers/submission_serializer.py:111
 msgid "project.error.submissions.no_files"
 msgstr "The submission is empty."
 
@@ -236,39 +240,39 @@ msgstr "The teacher was successfully added."
 msgid "teachers.success.destroy"
 msgstr "The teacher was successfully destroyed."
 
-#: views/course_view.py:137
+#: views/course_view.py:136
 msgid "courses.success.assistants.add"
 msgstr "The assistant was successfully added to the course."
 
-#: views/course_view.py:164
+#: views/course_view.py:163
 msgid "courses.success.assistants.remove"
 msgstr "The assistant was successfully removed from the course."
 
-#: views/course_view.py:226
+#: views/course_view.py:225
 msgid "courses.success.students.add"
 msgstr "The student was successfully added to the course."
 
-#: views/course_view.py:247
+#: views/course_view.py:246
 msgid "courses.success.students.remove"
 msgstr "The student was successfully removed from the course."
 
-#: views/course_view.py:292
+#: views/course_view.py:291
 msgid "courses.success.teachers.add"
 msgstr "The teacher was successfully added to the course."
 
-#: views/course_view.py:316
+#: views/course_view.py:315
 msgid "courses.success.teachers.remove"
 msgstr "The teacher was successfully removed from the course."
 
-#: views/group_view.py:74
+#: views/group_view.py:73
 msgid "group.success.students.add"
 msgstr "The student was successfully added to the group."
 
-#: views/group_view.py:94
+#: views/group_view.py:93
 msgid "group.success.students.remove"
 msgstr "The student was successfully removed from the group."
 
-#: views/group_view.py:113
+#: views/group_view.py:112
 msgid "group.success.submissions.add"
 msgstr "The submission was successfully added to the group."
 
@@ -296,6 +300,6 @@ msgstr "No zip file available."
 msgid "extra_check_result.download.log"
 msgstr "No log file available."
 
-#: views/submission_view.py:60
+#: views/submission_view.py:59
 msgid "extra_check_result.download.artifact"
 msgstr "No artifact available."
diff --git a/backend/api/models/project.py b/backend/api/models/project.py
index ceb786c1..d1d250c6 100644
--- a/backend/api/models/project.py
+++ b/backend/api/models/project.py
@@ -76,6 +76,11 @@ def deadline_passed(self):
         now = timezone.now()
         return now > self.deadline
 
+    def has_started(self):
+        """Returns True if the project has started."""
+        now = timezone.now()
+        return now >= self.start_date
+
     def is_archived(self):
         """Returns True if a project is archived."""
         return self.archived
diff --git a/backend/api/serializers/group_serializer.py b/backend/api/serializers/group_serializer.py
index b62102c7..726a0a80 100644
--- a/backend/api/serializers/group_serializer.py
+++ b/backend/api/serializers/group_serializer.py
@@ -81,10 +81,6 @@ def validate(self, attrs):
         group: Group = self.context["group"]
         student: Student = attrs["student"]
 
-        # Make sure a student can't join if groups are locked
-        if group.project.is_groups_locked():
-            raise ValidationError(gettext("group.errors.locked"))
-
         # Make sure the group is not already full
         if group.is_full():
             raise ValidationError(gettext("group.errors.full"))
diff --git a/backend/api/serializers/submission_serializer.py b/backend/api/serializers/submission_serializer.py
index adf5f42e..9683ac24 100644
--- a/backend/api/serializers/submission_serializer.py
+++ b/backend/api/serializers/submission_serializer.py
@@ -98,6 +98,9 @@ def validate(self, attrs):
         group: Group = self.context["group"]
         project: Project = group.project
 
+        if not project.has_started():
+            raise ValidationError(_("project.error.submissions.project_not_started"))
+
         # Check if the project's deadline is not passed.
         if project.deadline_passed():
             raise ValidationError(_("project.error.submissions.past_project"))
diff --git a/backend/data/fixtures/realistic/projects/0/0/checks/generate_gibberish.sh b/backend/data/fixtures/realistic/projects/0/0/checks/generate_gibberish.sh
index 9690ec1e..2deb94d8 100755
--- a/backend/data/fixtures/realistic/projects/0/0/checks/generate_gibberish.sh
+++ b/backend/data/fixtures/realistic/projects/0/0/checks/generate_gibberish.sh
@@ -19,4 +19,4 @@ done
 
 # Generate an artifact
 
-wget https://golang.org/doc/gopher/modelsheet.jpg -P artifacts
+wget https://upload.wikimedia.org/wikipedia/commons/5/5e/Logo_UGent_NL_RGB_2400_kleur-op-wit.png -P artifacts
diff --git a/development.sh b/development.sh
index 5a83cf9d..df298669 100755
--- a/development.sh
+++ b/development.sh
@@ -134,7 +134,6 @@ if [ "$data" != "" ]; then
   docker-compose -f development.yml up -d backend redis celery
 
   echo "Clearing, Migrating & Populating the database"
-  # We have nog fixtures for notification yet.
   docker-compose -f development.yml run backend sh -c "python manage.py flush --no-input; python manage.py migrate; python manage.py loaddata notifications/fixtures/$data/*; python manage.py loaddata authentication/fixtures/$data/*; python manage.py loaddata api/fixtures/$data/*;"
 
   echo "Stopping the services"