diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 90da86be..4a2c56d7 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -107,7 +107,7 @@ jobs:
           pip check
       - name: Run the tests
         run: |
-          pytest -vv || pytest -vv --lf
+          pytest -vv -W default || pytest -vv --lf
 
   make_sdist:
     name: Make SDist
diff --git a/jupyter_server_ydoc/ydoc.py b/jupyter_server_ydoc/ydoc.py
index 4103e3f7..153ac492 100644
--- a/jupyter_server_ydoc/ydoc.py
+++ b/jupyter_server_ydoc/ydoc.py
@@ -247,10 +247,6 @@ def on_document_change(self, event):
                 return
         except Exception:
             pass
-        # unobserve and observe again because the structure of the document may have changed
-        # e.g. a new cell added to a notebook
-        self.room.document.unobserve()
-        self.room.document.observe(self.on_document_change)
         if self.saving_document is not None and not self.saving_document.done():
             # the document is being saved, cancel that
             self.saving_document.cancel()