diff --git a/docs/requirements.txt b/docs/requirements.txt
index 7907e404f2..6499377054 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -1,5 +1,5 @@
 bqplot
-ipykernel
+ipykernel<6
 jupyter_client
 matplotlib
 nbsphinx>=0.5