diff --git a/.github/workflows/update-lean-nightly-version.yml b/.github/workflows/update-lean-nightly-version.yml
index 81d8e09e4..d24ed01c8 100644
--- a/.github/workflows/update-lean-nightly-version.yml
+++ b/.github/workflows/update-lean-nightly-version.yml
@@ -16,6 +16,7 @@ jobs:
         uses: actions/checkout@v4
         with:
           token: ${{secrets.PAT}}
+          ref: nightly-testing
 
       - name: Install elan 🕑
         run: |
diff --git a/lean-toolchain b/lean-toolchain
index a6b844a5c..18640c8b0 100644
--- a/lean-toolchain
+++ b/lean-toolchain
@@ -1 +1 @@
-leanprover/lean4:nightly-2026-06-10
+leanprover/lean4:v4.31.0