diff --git a/joeflow/models.py b/joeflow/models.py
index df067fa..266091f 100644
--- a/joeflow/models.py
+++ b/joeflow/models.py
@@ -137,7 +137,7 @@ def urls(cls):
                 if isinstance(node, BaseCreateView):
                     route = "{name}/".format(name=name)
                 else:
-                    route = "{name}/<pk>/".format(name=name)
+                    route = "{name}/<int:pk>/".format(name=name)
                 urls.append(
                     path(
                         route + node.path,
@@ -147,12 +147,12 @@ def urls(cls):
                 )
         if cls.detail_view:
             urls.append(
-                path("<pk>/", cls.detail_view.as_view(model=cls), name="detail")
+                path("<int:pk>/", cls.detail_view.as_view(model=cls), name="detail")
             )
         if cls.override_view:
             urls.append(
                 path(
-                    "<pk>/override",
+                    "<int:pk>/override",
                     cls.override_view.as_view(model=cls),
                     name="override",
                 )
diff --git a/tests/test_models.py b/tests/test_models.py
index dc82286..4ecad08 100644
--- a/tests/test_models.py
+++ b/tests/test_models.py
@@ -249,6 +249,10 @@ class Meta:
             "override",
         }
 
+    def test_urls__none_int_pk_mismatch(self, client):
+        response = client.get("/shipment/test/")
+        assert response.status_code == 404
+
 
 class TestTaskQuerySet:
     def test_scheduled(self, db):