diff --git a/src/jupyter_contrib_nbextensions/nbconvert_support/collapsible_headings.py b/src/jupyter_contrib_nbextensions/nbconvert_support/collapsible_headings.py
index 7e6bcf520..7e139d304 100644
--- a/src/jupyter_contrib_nbextensions/nbconvert_support/collapsible_headings.py
+++ b/src/jupyter_contrib_nbextensions/nbconvert_support/collapsible_headings.py
@@ -3,7 +3,10 @@
 import json
 import os
 
-from notebook.services.config import ConfigManager
+try:
+    from notebook.services.config import ConfigManager
+except ModuleNotFoundError:
+    from jupyter_server.services.config import ConfigManager
 
 from jupyter_contrib_nbextensions import __file__ as contrib_init
 
diff --git a/src/jupyter_contrib_nbextensions/nbconvert_support/execute_time.py b/src/jupyter_contrib_nbextensions/nbconvert_support/execute_time.py
index 53b920dbd..4a13f1903 100644
--- a/src/jupyter_contrib_nbextensions/nbconvert_support/execute_time.py
+++ b/src/jupyter_contrib_nbextensions/nbconvert_support/execute_time.py
@@ -10,8 +10,11 @@
     # notebook >= 5.0.0-rc1
     import notebook._tz as nbtz
 except ImportError:
-    # notebook < 5.0.0-rc1
-    import notebook.services.contents.tz as nbtz
+    try:
+        # notebook < 5.0.0-rc1
+        import notebook.services.contents.tz as nbtz
+    except ModuleNotFoundError:
+        import jupyter_server._tz as nbtz
 
 
 class ExecuteTimePreprocessor(ExecutePreprocessor):