diff --git a/src/c3nav/mapdata/migrations/0063_descriptions_unique_together.py b/src/c3nav/mapdata/migrations/0063_descriptions_unique_together.py
new file mode 100644
index 00000000..7b3b4473
--- /dev/null
+++ b/src/c3nav/mapdata/migrations/0063_descriptions_unique_together.py
@@ -0,0 +1,23 @@
+# -*- coding: utf-8 -*-
+# Generated by Django 1.11.7 on 2017-12-19 00:59
+from __future__ import unicode_literals
+
+from django.db import migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('mapdata', '0062_typos'),
+    ]
+
+    operations = [
+        migrations.AlterUniqueTogether(
+            name='crossdescription',
+            unique_together=set([('space', 'origin_space', 'target_space')]),
+        ),
+        migrations.AlterUniqueTogether(
+            name='leavedescription',
+            unique_together=set([('space', 'target_space')]),
+        ),
+    ]
diff --git a/src/c3nav/mapdata/models/geometry/space.py b/src/c3nav/mapdata/models/geometry/space.py
index d4daa60b..384af92a 100644
--- a/src/c3nav/mapdata/models/geometry/space.py
+++ b/src/c3nav/mapdata/models/geometry/space.py
@@ -256,6 +256,9 @@ class LeaveDescription(models.Model):
         verbose_name = _('Leave description')
         verbose_name_plural = _('Leave descriptions')
         default_related_name = 'leave_descriptions'
+        unique_together = (
+            ('space', 'target_space')
+        )
 
     @cached_property
     def title(self):
@@ -277,6 +280,9 @@ class CrossDescription(models.Model):
         verbose_name = _('Cross description')
         verbose_name_plural = _('Cross descriptions')
         default_related_name = 'cross_descriptions'
+        unique_together = (
+            ('space', 'origin_space', 'target_space')
+        )
 
     @cached_property
     def title(self):