diff --git a/docs/requirements.txt b/docs/requirements.txt
index 4bde8aa..caaa865 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -2,7 +2,7 @@
 canonical-sphinx>=0.5.1
 
 # Extensions previously auto-loaded by canonical-sphinx
-myst-parser
+myst-parser~=4.0
 sphinx-autobuild
 sphinx-design
 sphinx-notfound-page