diff --git a/src/pyquickhelper/sphinxext/sphinx_md_builder.py b/src/pyquickhelper/sphinxext/sphinx_md_builder.py
index 65afe269..e9768dae 100644
--- a/src/pyquickhelper/sphinxext/sphinx_md_builder.py
+++ b/src/pyquickhelper/sphinxext/sphinx_md_builder.py
@@ -977,8 +977,9 @@ def depart_todo_node(self, node):
         self.depart_admonition(node)
 
     def unknown_visit(self, node):
-        raise NotImplementedError(
-            "Unknown node: '{0}' - '{1}'".format(node.__class__.__name__, node))
+        logger = logging.getLogger("MdBuilder")
+        logger.warning("[md] unknown visit node: '{0}' - '{1}'".format(
+                node.__class__.__name__, node))
 
 
 class MdBuilder(Builder):
diff --git a/src/pyquickhelper/sphinxext/sphinx_rst_builder.py b/src/pyquickhelper/sphinxext/sphinx_rst_builder.py
index e416b998..e14da079 100644
--- a/src/pyquickhelper/sphinxext/sphinx_rst_builder.py
+++ b/src/pyquickhelper/sphinxext/sphinx_rst_builder.py
@@ -1097,8 +1097,9 @@ def unknown_visit(self, node):
                          }:
             # due to jupyter_sphinx
             return
-        raise NotImplementedError(
-            "Unknown node: '{0}' - '{1}'".format(node.__class__.__name__, node))
+        logger = logging.getLogger("RstBuilder")
+        logger.warning("[rst] unknown visit node: '{0}' - '{1}'".format(
+                node.__class__.__name__, node))
 
     def unknown_departure(self, node):
         classname = node.__class__.__name__
@@ -1109,8 +1110,9 @@ def unknown_departure(self, node):
                          }:
             # due to jupyter_sphinx
             return
-        raise NotImplementedError(
-            "Unknown node: '{0}' - '{1}'".format(node.__class__.__name__, node))
+        logger = logging.getLogger("RstBuilder")
+        logger.warning("[rst] unknown depart node: '{0}' - '{1}'".format(
+                node.__class__.__name__, node))
 
 
 class _BodyPlaceholder: