diff --git a/.github/workflows/opam.yml b/.github/workflows/opam.yml
index a7e041f5..5e26765c 100644
--- a/.github/workflows/opam.yml
+++ b/.github/workflows/opam.yml
@@ -51,7 +51,7 @@ jobs:
         run: |
           opam install --with-test ./qcheck-multicoretests-util.opam ./qcheck-lin.opam ./qcheck-stm.opam
 
-      - name:
+      - name: Test installation of the Eio OPAM packages
         if: matrix.test-eio == true
         run: |
           opam install --with-test ./qcheck-stm-eio.opam ./qcheck-lin-eio.opam
diff --git a/dune-project b/dune-project
index 8f04ae8c..b95b2352 100644
--- a/dune-project
+++ b/dune-project
@@ -44,9 +44,10 @@ sequential and parallel tests against a declarative model.")
         "model-based testing" "parallel testing"))
  (depopts base-domains)
  (depends
-  (ocaml (>= 4.12))
+  (ocaml (>= 5.1))
   (qcheck-core           (>= "0.90"))
   (eio  (>= "1.0"))
+  (eio_main (and (>= "1.0") :with-test))
   (qcheck-multicoretests-util (= :version))
   (qcheck-stm           (= :version))))
 
@@ -76,9 +77,10 @@ and explained by some sequential interleaving.")
  (tags ("test" "property" "qcheck" "quickcheck" "parallelism" "sequential consistency"))
  (depopts base-domains)
  (depends
-  (ocaml (>= 4.12))
+  (ocaml (>= 5.1))
   (qcheck-core           (>= "0.90"))
   (eio  (>= "1.0"))
+  (eio_main (and (>= "1.0") :with-test))
   (qcheck-multicoretests-util (= :version))
   (qcheck-lin           (= :version))))
 
diff --git a/qcheck-lin-eio.opam b/qcheck-lin-eio.opam
index 04da3b7d..bd301caf 100644
--- a/qcheck-lin-eio.opam
+++ b/qcheck-lin-eio.opam
@@ -22,9 +22,10 @@ homepage: "https://github.com/ocaml-multicore/multicoretests"
 bug-reports: "https://github.com/ocaml-multicore/multicoretests/issues"
 depends: [
   "dune" {>= "3.18"}
-  "ocaml" {>= "4.12"}
+  "ocaml" {>= "5.1"}
   "qcheck-core" {>= "0.90"}
   "eio" {>= "1.0"}
+  "eio_main" {>= "1.0" & with-test}
   "qcheck-multicoretests-util" {= version}
   "qcheck-lin" {= version}
   "odoc" {with-doc}
diff --git a/qcheck-stm-eio.opam b/qcheck-stm-eio.opam
index a70b6b72..05cc46a0 100644
--- a/qcheck-stm-eio.opam
+++ b/qcheck-stm-eio.opam
@@ -22,9 +22,10 @@ homepage: "https://github.com/ocaml-multicore/multicoretests"
 bug-reports: "https://github.com/ocaml-multicore/multicoretests/issues"
 depends: [
   "dune" {>= "3.18"}
-  "ocaml" {>= "4.12"}
+  "ocaml" {>= "5.1"}
   "qcheck-core" {>= "0.90"}
   "eio" {>= "1.0"}
+  "eio_main" {>= "1.0" & with-test}
   "qcheck-multicoretests-util" {= version}
   "qcheck-stm" {= version}
   "odoc" {with-doc}
diff --git a/src/neg_tests/dune b/src/neg_tests/dune
index 885e2780..d41d7aa1 100644
--- a/src/neg_tests/dune
+++ b/src/neg_tests/dune
@@ -3,7 +3,6 @@
 (library
  (name stm_tests_ref_spec)
  (modules stm_tests_ref_spec)
- (package multicoretests)
  (libraries qcheck-core qcheck-stm.stm)
 )
 
@@ -43,6 +42,8 @@
  (name stm_tests_ref_eio)
  (modules stm_tests_ref_eio)
  (package qcheck-stm-eio)
+ ; Eio is not a dependency of multicoretests: skip when it is missing
+ (build_if %{lib-available:eio_main})
  (libraries stm_tests_ref_spec qcheck-stm-eio.domain eio eio_main)
  ; Hangs with the linux backend
  (action
@@ -53,7 +54,6 @@
 (library
  (name CList)
  (modules CList)
- (package multicoretests)
 )
 
 (test
@@ -84,6 +84,8 @@
  (name stm_tests_clist_eio)
  (modules stm_tests_clist_spec stm_tests_clist_eio)
  (package qcheck-stm-eio)
+ ; Eio is not a dependency of multicoretests: skip when it is missing
+ (build_if %{lib-available:eio_main})
  (libraries CList qcheck-stm-eio.domain eio eio_main)
  ; Hangs with the linux backend
  (action
@@ -96,14 +98,12 @@
 (library
  (name lin_tests_common)
  (modules lin_tests_common)
- (package multicoretests)
  (libraries CList qcheck-lin.lin)
 )
 
 (library
  (name lin_internal_tests_common)
  (modules lin_internal_tests_common)
- (package multicoretests)
  (libraries CList qcheck-lin.lin)
 )
 
@@ -138,6 +138,8 @@
  (name lin_tests_eio)
  (modules lin_tests_eio)
  (package qcheck-lin-eio)
+ ; Eio is not a dependency of multicoretests: skip when it is missing
+ (build_if %{lib-available:eio_main})
  (flags (:standard -w -27))
  (libraries lin_tests_common qcheck-lin-eio.domain eio eio_main)
  ; Hangs with the linux backend
@@ -182,6 +184,8 @@
  (name lin_internal_tests_eio)
  (modules lin_internal_tests_eio)
  (package qcheck-lin-eio)
+ ; Eio is not a dependency of multicoretests: skip when it is missing
+ (build_if %{lib-available:eio_main})
  (flags (:standard -w -27))
  (libraries lin_internal_tests_common qcheck-lin-eio.domain eio eio_main)
  ; (setenv EIO_BACKEND posix (run %{test} --verbose))