diff --git a/requirements.txt b/requirements.txt
index 7cfa743..f39d86e 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -29,6 +29,8 @@ nbmerge
 # this part is for readthedocs or similar
 #
 ipypublish[sphinx]
+# nov 2020: latest panflute 2.0.5 breaks our build
+panflute==1.12.5
 sphinx-rtd-theme
 jupytext
 jupyter_client
diff --git a/slides/conf.py b/slides/conf.py
index 6de4320..b8d4bef 100644
--- a/slides/conf.py
+++ b/slides/conf.py
@@ -14,7 +14,11 @@
 
 master_doc = "index"
 
-source_suffix = ['.rst']
+source_suffix = {
+    '.rst': 'restructuredtext',
+#    '.ipynb': 'jupyter_notebook',
+    '.py': 'jupyter_notebook'
+}
 
 exclude_patterns = ['_build', 'build', '**.ipynb_checkpoints']