diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index 4fe7c5c087a6906420ef8e212266571a3abc6984..4de936f758f38e8dca36db3faffd78dcafcf52c4 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -1,6 +1,14 @@
 Changelog
 =========
 
+Unreleased
+----------
+
+Fixed
+~~~~~
+
+* Unique constraints for breaks and substitutions were too tight
+
 `2.0b0`_ - 2021-05-21
 ---------------------
 
diff --git a/aleksis/apps/chronos/migrations/0007_unique_constraints.py b/aleksis/apps/chronos/migrations/0007_unique_constraints.py
index 754c3ae1c1c9c7a8a4e3ab6f616a459cf65d5298..048da7fde020013012c04922859e89f5b9e5ddfc 100644
--- a/aleksis/apps/chronos/migrations/0007_unique_constraints.py
+++ b/aleksis/apps/chronos/migrations/0007_unique_constraints.py
@@ -52,11 +52,11 @@ class Migration(migrations.Migration):
         ),
         migrations.AddConstraint(
             model_name='break',
-            constraint=models.UniqueConstraint(fields=('site_id', 'short_name'), name='unique_short_name_per_site_break'),
+            constraint=models.UniqueConstraint(fields=('validity', 'short_name'), name='unique_short_name_per_site_break'),
         ),
         migrations.AddConstraint(
             model_name='lessonsubstitution',
-            constraint=models.UniqueConstraint(fields=('lesson_period', 'week'), name='unique_period_per_week'),
+            constraint=models.UniqueConstraint(fields=('lesson_period', 'week', 'year'), name='unique_period_per_week'),
         ),
         migrations.AddConstraint(
             model_name='room',
diff --git a/aleksis/apps/chronos/models.py b/aleksis/apps/chronos/models.py
index 97f701ee1c3bc2fd591a7572dff96e3844c03654..07dc3fda0bd8429f7c335093bbe0b2ae3a07b723 100644
--- a/aleksis/apps/chronos/models.py
+++ b/aleksis/apps/chronos/models.py
@@ -451,7 +451,7 @@ class LessonSubstitution(ExtensibleModel, TeacherPropertiesMixin, WeekRelatedMix
             ),
             # Heads up: Link to period implies uniqueness per site
             models.UniqueConstraint(
-                fields=["lesson_period", "week"], name="unique_period_per_week"
+                fields=["lesson_period", "week", "year"], name="unique_period_per_week"
             ),
         ]
         indexes = [
@@ -866,7 +866,7 @@ class Break(ValidityRangeRelatedExtensibleModel):
         verbose_name_plural = _("Breaks")
         constraints = [
             models.UniqueConstraint(
-                fields=["site_id", "short_name"], name="unique_short_name_per_site_break"
+                fields=["validity", "short_name"], name="unique_short_name_per_site_break"
             ),
         ]