diff --git a/.github/workflows/doc.yml b/.github/workflows/doc.yml
index fdea90731..21d39c19d 100644
--- a/.github/workflows/doc.yml
+++ b/.github/workflows/doc.yml
@@ -25,7 +25,7 @@ jobs:
     - name: setup ocaml
       uses: avsm/setup-ocaml@v1
       with:
-        ocaml-version: 4.10.1
+        ocaml-version: 4.09.1
 
     - name: install deps
       run: |