diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index d66d007..1210d42 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -51,6 +51,11 @@ jobs:
           ocaml-compiler: ${{ matrix.ocaml-compiler }}
           allow-prerelease-opam: true
 
+      - name: set ocamlversion
+        run: echo "ocamlversion=$(opam exec -- ocamlc -version)" >> $GITHUB_OUTPUT
+        id: conf
+        shell: bash
+
       - run: opam install . --with-test --deps-only
 
       - run: opam exec -- make test
@@ -63,13 +68,13 @@ jobs:
       - run: opam exec -- opam install -v ocamlbuild
       - run: opam exec -- opam install -v menhir
       - run: opam exec -- opam install -v camlp4
-        if: (! startsWith(matrix.ocaml-compiler, '5.2'))
+        if: ${{ ! startsWith(steps.conf.outputs.ocamlversion, '5.2.') }}
       - run: opam exec -- make test-external
-        if: (! startsWith(matrix.ocaml-compiler, '5.2'))
-      - run: opam exec -- opam install -v mtime.1.0.0 # this tests topkg, with stub libraries
+        if: ${{ ! startsWith(steps.conf.outputs.ocamlversion, '5.2.') }}
+      - run: opam exec -- opam install -v mtime.1.4.0 # this tests topkg, with stub libraries
       - run: opam exec -- opam install -v inotify.2.3 # this tests oasis, with stub libraries
-        if: (! startsWith(matrix.ocaml-compiler, '5')) && runner.os != 'Windows'
+        if: ${{ ! startsWith(steps.conf.outputs.ocamlversion, '5.') && runner.os != 'Windows' }}
       - run: opam exec -- opam install -v cpuid.0.1.1 # this tests the ocb-stubblr plugin
         if: runner.os != 'Windows'
       - run: opam exec -- opam install -v shcaml.0.2.1 # this tests the cppo plugin
-        if: (! startsWith(matrix.ocaml-compiler, '5')) && runner.os != 'Windows'
+        if: ${{ ! startsWith(steps.conf.outputs.ocamlversion, '5.') && runner.os != 'Windows' }}