diff --git a/aleksis/apps/alsijil/migrations/0008_global_permissions.py b/aleksis/apps/alsijil/migrations/0008_global_permissions.py
index 609fc703c60cee7770c06d819b06b309a22c56af..c65913c18e71085381ebd3b24dda63e747c8aa8b 100644
--- a/aleksis/apps/alsijil/migrations/0008_global_permissions.py
+++ b/aleksis/apps/alsijil/migrations/0008_global_permissions.py
@@ -17,6 +17,7 @@ class Migration(migrations.Migration):
                 ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
                 ('extended_data', models.JSONField(default=dict, editable=False)),
             ],
+            "default_permissions": (),
             options={
                 'permissions': (('view_week', 'Can view week overview'), ('register_absence', 'Can register absence'), ('list_personal_note_filters', 'Can list all personal note filters')),
                 'managed': False,
diff --git a/aleksis/apps/alsijil/models.py b/aleksis/apps/alsijil/models.py
index 4ae43ea60de19e01ec1c7b874ab30747c195ffce..f1f65ac936cd18b4f54c4cc6a5e66b662050cc90 100644
--- a/aleksis/apps/alsijil/models.py
+++ b/aleksis/apps/alsijil/models.py
@@ -31,7 +31,7 @@ from aleksis.apps.alsijil.managers import (
 from aleksis.apps.chronos.managers import GroupPropertiesMixin
 from aleksis.apps.chronos.mixins import WeekRelatedMixin
 from aleksis.apps.chronos.models import Event, ExtraLesson, LessonPeriod
-from aleksis.core.mixins import ExtensibleModel
+from aleksis.core.mixins import ExtensibleModel, GlobalPermissionModel
 from aleksis.core.models import SchoolTerm
 from aleksis.core.util.core_helpers import get_site_preferences
 from aleksis.core.util.model_helpers import ICONS
@@ -447,7 +447,7 @@ class GroupRoleAssignment(GroupPropertiesMixin, ExtensibleModel):
         verbose_name_plural = _("Group role assignments")
 
 
-class AlsijilGlobalPermissions(ExtensibleModel):
+class AlsijilGlobalPermissions(GlobalPermissionModel):
     class Meta:
         managed = False
         permissions = (
diff --git a/aleksis/apps/alsijil/templates/alsijil/class_register/lesson.html b/aleksis/apps/alsijil/templates/alsijil/class_register/lesson.html
index f21d7686acb763c6f63942dcab91517020b7e0e2..13e781bfb24e3dab3184aa0145dadde7dffd3987 100644
--- a/aleksis/apps/alsijil/templates/alsijil/class_register/lesson.html
+++ b/aleksis/apps/alsijil/templates/alsijil/class_register/lesson.html
@@ -114,11 +114,13 @@
                 <a href="#personal-notes">{% trans "Personal notes" %}</a>
               </li>
             {% endif %}
-            {% has_perm "alsijil.view_lessondocumentation" user register_object.prev as can_view_prev_lesson_documentation %}
-            {% if register_object.prev.get_lesson_documentation and can_view_prev_lesson_documentation %}
-              <li class="tab">
-                <a href="#previous-lesson">{% trans "Previous lesson" %}</a>
-              </li>
+            {% if prev_lesson %}
+              {% has_perm "alsijil.view_lessondocumentation" user prev_lesson as can_view_prev_lesson_documentation %}
+              {% if prev_lesson.get_lesson_documentation and can_view_prev_lesson_documentation %}
+                <li class="tab">
+                  <a href="#previous-lesson">{% trans "Previous lesson" %}</a>
+                </li>
+              {% endif %}
             {% endif %}
             {% if group_roles %}
               <li class="tab">
@@ -172,7 +174,7 @@
           </div>
         </div>
 
-        {% with prev_lesson=register_object.prev prev_doc=prev_lesson.get_lesson_documentation %}
+        {% with prev_doc=prev_lesson.get_lesson_documentation %}
           {% with absences=prev_lesson.get_absences tardinesses=prev_lesson.get_tardinesses extra_marks=prev_lesson.get_extra_marks %}
             {% has_perm "alsijil.view_lessondocumentation" user prev_lesson as can_view_prev_lesson_documentation %}
             {% if prev_doc and can_view_prev_lesson_documentation %}
diff --git a/aleksis/apps/alsijil/util/alsijil_helpers.py b/aleksis/apps/alsijil/util/alsijil_helpers.py
index b5879b1f2ddcb79dbe336c9c4285ddccc30f23f6..20d1a94ab12811a2aa8e8b0664746bd4dbaed7bd 100644
--- a/aleksis/apps/alsijil/util/alsijil_helpers.py
+++ b/aleksis/apps/alsijil/util/alsijil_helpers.py
@@ -210,11 +210,7 @@ def _generate_dicts_for_lesson_periods(
                 ):
                     continue
 
-                teachers = (
-                    sub.teacher_names
-                    if sub and sub.teachers.all()
-                    else lesson_period.lesson.teacher_names
-                )
+                teachers = lesson_period.teacher_names
                 if (
                     filter_dict.get("subject")
                     and filter_dict.get("subject") != lesson_period.get_subject()