diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 721060d95..9593edd6d 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -21,7 +21,7 @@ jobs:
       - uses: actions/cache@v2
         with:
           path: ~/.opam
-          key: ${{ matrix.os }}-opam-${{ matrix.ocaml-version }}-flambda-musl-v5
+          key: ${{ matrix.os }}-opam-${{ matrix.ocaml-version }}-flambda-musl-v6
 
       - name: Install musl-compatible kernel headers
         run: |