diff --git a/CHANGELOG.md b/CHANGELOG.md
index 27ff8270..ecfbac20 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,10 +7,11 @@ Jupytext ChangeLog
 **Fixed**
 - The `rst2md` tests have been fixed by requiring `sphinx<8` ([#1266](https://github.com/mwouts/jupytext/issues/1266))
 - Some dependencies of the JupyterLab extensions were updated ([#1272](https://github.com/mwouts/jupytext/issues/1272), [#1273](https://github.com/mwouts/jupytext/issues/1273), [#1280](https://github.com/mwouts/jupytext/issues/1280), [#1285](https://github.com/mwouts/jupytext/issues/1285), [#1290](https://github.com/mwouts/jupytext/issues/1290))
-- The pre-commit hook is now compatible with log.showsignature=True (#1281). Thanks to [Justin Lecher](https://github.com/jlec) for this fix.
+- The pre-commit hook is now compatible with log.showsignature=True ([#1281](https://github.com/mwouts/jupytext/issues/1281)). Thanks to [Justin Lecher](https://github.com/jlec) for this fix.
 
 **Added**
 - Jupytext is now tested with Python 3.13 ([#1242](https://github.com/mwouts/jupytext/issues/1242)). Thanks to [Jerry James](https://github.com/jamesjer) for the suggested fixes!
+- The extension of a notebook piped into stdin will be taken in the notebook metadata ([#1282](https://github.com/mwouts/jupytext/issues/1282))
 
 
 1.16.4 (2024-07-12)
diff --git a/environment.yml b/environment.yml
index 52f63845..b2b30d51 100644
--- a/environment.yml
+++ b/environment.yml
@@ -1,6 +1,5 @@
 name: jupytext-dev
 channels:
-  - defaults
   - conda-forge
 dependencies:
   - python>=3.8
diff --git a/jupyterlab/packages/jupyterlab-jupytext-extension/CHANGELOG.md b/jupyterlab/packages/jupyterlab-jupytext-extension/CHANGELOG.md
index 3a7c3316..3716cefa 100644
--- a/jupyterlab/packages/jupyterlab-jupytext-extension/CHANGELOG.md
+++ b/jupyterlab/packages/jupyterlab-jupytext-extension/CHANGELOG.md
@@ -1,3 +1,7 @@
+# 1.4.3+dev
+
+Some dependencies of the JupyterLab extensions were updated ([#1272](https://github.com/mwouts/jupytext/issues/1272), [#1273](https://github.com/mwouts/jupytext/issues/1273), [#1280](https://github.com/mwouts/jupytext/issues/1280), [#1285](https://github.com/mwouts/jupytext/issues/1285), [#1290](https://github.com/mwouts/jupytext/issues/1290))
+
 # 1.4.3 (2024-05-05)
 
 - JupyterLab's dependency `ejs` was updated from 3.1.9 to 3.1.10 ([#1231](https://github.com/mwouts/jupytext/issues/1231))
diff --git a/src/jupytext/formats.py b/src/jupytext/formats.py
index efed28cd..91c3b773 100644
--- a/src/jupytext/formats.py
+++ b/src/jupytext/formats.py
@@ -418,10 +418,14 @@ def check_file_version(notebook, source_path, outputs_path):
     if not insert_or_test_version_number():
         return
 
-    _, ext = os.path.splitext(source_path)
-    assert not ext.endswith(".ipynb"), "source_path={} should be a text file".format(
-        source_path
-    )
+    if source_path == "-":
+        # https://github.com/mwouts/jupytext/issues/1282
+        ext = notebook.metadata["jupytext"]["text_representation"]["extension"]
+    else:
+        _, ext = os.path.splitext(source_path)
+        assert not ext.endswith(
+            ".ipynb"
+        ), "source_path={} should be a text file".format(source_path)
 
     version = (
         notebook.metadata.get("jupytext", {})