diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index b15bdfb..073ac0a 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -19,8 +19,8 @@ jobs:
           - windows-latest
           - macos-latest
         ocaml-compiler:
-          - 4.14.x
-          - 5.2.x
+          - "4.14"
+          - "5.2"
 
     runs-on: ${{ matrix.os }}
 
@@ -35,9 +35,12 @@ jobs:
             default: https://github.com/hhugo/opam-repository.git#gmp-mingw
           ocaml-compiler: ${{ matrix.ocaml-compiler }}
           dune-cache: true
-          cache-prefix: "z1"
+          cache-prefix: "z2"
           allow-prerelease-opam: true
 
+      - run: bash -c "rm -rf D:/cygwin/var/log"
+        if: runner.os = "Windows"
+
       - run: opam install -v . --with-test --deps-only
 
       - name: configure tree