diff --git a/src/c3nav/editor/models/changeset.py b/src/c3nav/editor/models/changeset.py
index 5f0353c2..3a1804be 100644
--- a/src/c3nav/editor/models/changeset.py
+++ b/src/c3nav/editor/models/changeset.py
@@ -6,6 +6,8 @@ from django.apps import apps
 from django.conf import settings
 from django.db import models, transaction
 from django.urls import reverse
+from django.utils.http import int_to_base36
+from django.utils.timezone import make_naive
 from django.utils.translation import ugettext_lazy as _
 from django.utils.translation import ungettext_lazy
 from rest_framework.exceptions import PermissionDenied
@@ -410,10 +412,18 @@ class ChangeSet(models.Model):
                 {'num': self.changed_objects_count})
 
     @property
-    def cache_key(self):
-        if self.pk is None:
-            return None
-        return str(self.pk)+'-'+str(self.last_change)
+    def updates_cache_key(self):
+        pk, mapupdate = MapUpdate.last_update()
+        last_update = self.created if self.last_update_id is None else self.last_update.datetime
+        return (MapUpdate.cache_key() + '_' + int_to_base36(self.last_update_id or 0) + '_' +
+                int_to_base36(int(make_naive(last_update).timestamp())))
+
+    @property
+    def changes_cache_key(self):
+        pk, mapupdate = MapUpdate.last_update()
+        last_change = self.created if self.last_change_id is None else self.last_change.datetime
+        return (MapUpdate.cache_key() + '_' + int_to_base36(self.last_change_id or 0) + '_' +
+                int_to_base36(int(make_naive(last_change).timestamp())))
 
     def get_absolute_url(self):
         if self.pk is None:
diff --git a/src/c3nav/mapdata/models/update.py b/src/c3nav/mapdata/models/update.py
index 75621c2c..d2f1505a 100644
--- a/src/c3nav/mapdata/models/update.py
+++ b/src/c3nav/mapdata/models/update.py
@@ -3,6 +3,8 @@ from contextlib import contextmanager
 from django.conf import settings
 from django.core.cache import cache
 from django.db import models, transaction
+from django.utils.http import int_to_base36
+from django.utils.timezone import make_naive
 from django.utils.translation import ugettext_lazy as _
 
 
@@ -26,9 +28,14 @@ class MapUpdate(models.Model):
         if last_update is not None:
             return last_update
         with cls.lock():
-            last_update = cls.objects.latest().datetime
-            cache.set('mapdata:last_update', last_update, 900)
-        return last_update
+            last_update = cls.objects.latest()
+            cache.set('mapdata:last_update', (last_update.pk, last_update.datetime), 900)
+        return last_update.pk, last_update.datetime
+
+    @classmethod
+    def cache_key(cls):
+        pk, dt = cls.last_update()
+        return int_to_base36(pk)+'_'+int_to_base36(int(make_naive(dt).timestamp()))
 
     @classmethod
     @contextmanager
@@ -40,4 +47,4 @@ class MapUpdate(models.Model):
         if self.pk is not None:
             raise TypeError
         super().save(**kwargs)
-        cache.set('mapdata:last_update', self.datetime, 900)
+        cache.set('mapdata:last_update', (self.pk, self.datetime), 900)