diff --git a/evennia/typeclasses/managers.py b/evennia/typeclasses/managers.py
index c3902275f0..c27e5a04e7 100644
--- a/evennia/typeclasses/managers.py
+++ b/evennia/typeclasses/managers.py
@@ -197,6 +197,8 @@ class TypedObjectManager(idmapper.manager.SharedMemoryManager):
                 query.append(("db_key", key))
             if category:
                 query.append(("db_category", category))
+            else:
+                query.append(("db_category", None))
             return _Tag.objects.filter(**dict(query))
         else:
             # search only among tags stored on on this model
diff --git a/evennia/typeclasses/tests.py b/evennia/typeclasses/tests.py
index 04e37a28c2..198e3eb086 100644
--- a/evennia/typeclasses/tests.py
+++ b/evennia/typeclasses/tests.py
@@ -314,6 +314,23 @@ class TestTags(BaseEvenniaTest):
         self.obj1.tags.add("tagC", "categoryC")
         self.assertFalse(self.obj1.tags.has(category="categoryD"))
 
+    def test_tag_add_no_category__issue_2688(self):
+        """
+        Adding a tag without a category should create a new tag:None tag
+        rather than trying to update an existing tag:category tag.
+        """
+        # adding tag+category, creates tag+category entry
+        self.obj1.tags.add("testing", category="testing_category")
+        self.assertEqual(
+            self.obj1.tags.all(return_key_and_category=True), [("testing", "testing_category")]
+        )
+        # adding a new tag with no category should create a tag+None entry
+        self.obj1.tags.add("testing")
+        self.assertEqual(
+            self.obj1.tags.all(return_key_and_category=True),
+            [("testing", "testing_category"), ("testing", None)],
+        )
+
 
 class TestNickHandler(BaseEvenniaTest):
     """