diff --git a/umap/migrations/0018_datalayer_uuid.py b/umap/migrations/0018_datalayer_uuid.py
index 5f5f2add..9d0bbd23 100644
--- a/umap/migrations/0018_datalayer_uuid.py
+++ b/umap/migrations/0018_datalayer_uuid.py
@@ -25,10 +25,11 @@ class Migration(migrations.Migration):
             field=models.UUIDField(default=uuid.uuid4, editable=False, null=True),
         ),
         migrations.RunPython(gen_uuid, reverse_code=migrations.RunPython.noop),
-        migrations.AlterField("datalayer", name="id", field=models.CharField(max_length=100)),
+        migrations.AlterField("datalayer", name="id", field=models.CharField(max_length=100, null=True)),
         migrations.AlterField(
             model_name="datalayer",
             name="uuid",
             field=models.UUIDField(default=uuid.uuid4, editable=False, unique=True, primary_key=True),
         ),
+        # migrations.RemoveConstraint("datalayer", "")
     ]
diff --git a/umap/templatetags/umap_tags.py b/umap/templatetags/umap_tags.py
index 2349c579..b995df4f 100644
--- a/umap/templatetags/umap_tags.py
+++ b/umap/templatetags/umap_tags.py
@@ -3,6 +3,7 @@ from copy import copy
 
 from django import template
 from django.conf import settings
+from django.core.serializers.json import DjangoJSONEncoder
 
 register = template.Library()
 
@@ -25,7 +26,7 @@ def map_fragment(map_instance, **kwargs):
     page = kwargs.pop("page", None) or ""
     unique_id = prefix + str(page) + "_" + str(map_instance.pk)
     return {
-        "map_settings": json.dumps(map_settings),
+        "map_settings": json.dumps(map_settings, cls=DjangoJSONEncoder),
         "map": map_instance,
         "unique_id": unique_id,
     }
diff --git a/umap/tests/integration/test_collaborative_editing.py b/umap/tests/integration/test_collaborative_editing.py
index 29cd9b58..e22b0ee9 100644
--- a/umap/tests/integration/test_collaborative_editing.py
+++ b/umap/tests/integration/test_collaborative_editing.py
@@ -98,7 +98,7 @@ def test_collaborative_editing_create_markers(context, live_server, tilelayer):
         "name": "test datalayer",
         "inCaption": True,
         "editMode": "advanced",
-        "id": datalayer.pk,
+        "id": str(datalayer.pk),
         "permissions": {"edit_status": 1},
     }
 
@@ -116,7 +116,7 @@ def test_collaborative_editing_create_markers(context, live_server, tilelayer):
         "name": "test datalayer",
         "inCaption": True,
         "editMode": "advanced",
-        "id": datalayer.pk,
+        "id": str(datalayer.pk),
         "permissions": {"edit_status": 1},
     }
     expect(marker_pane_p1).to_have_count(4)
@@ -136,7 +136,7 @@ def test_collaborative_editing_create_markers(context, live_server, tilelayer):
         "name": "test datalayer",
         "inCaption": True,
         "editMode": "advanced",
-        "id": datalayer.pk,
+        "id": str(datalayer.pk),
         "permissions": {"edit_status": 1},
     }
     expect(marker_pane_p2).to_have_count(5)