diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 8fe240f9e137d9a95cd9a51302cea8ff7042f172..f5dbfc4508bb95718a118d7552b01b5aa7b600d9 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -3,13 +3,13 @@ stages:
 
 tests:
   stage: test
-  image: ocaml/opam@sha256:108b775e7bda2c6d3bddae61c9cdb003e40de746baf3a994e8f7b82d8301dd0a
+  image: ocaml/opam@sha256:013a26ccbaa8344b63274e335e2492c432cec1c3526b9ba888ab151abb2b4c25
   cache:
     key: $CI_COMMIT_REF_SLUG
     paths:
       - _opam
   script:
-  - if [ ! -d _opam ]; then echo "no local switch in the CI cache, we setup a new switch"; opam switch create --yes --no-install . ocaml-base-compiler.4.11.1; fi
+  - if [ ! -d _opam ]; then echo "no local switch in the CI cache, we setup a new switch"; opam switch create --yes --no-install . ocaml-base-compiler.4.13.1; fi
   - eval $(opam env)
   - sudo apt-get update
   - sudo apt install -y protobuf-compiler
diff --git a/caisar.opam b/caisar.opam
index 04f8e424d3b5f7d920482b6ac14e88b70f5d102d..a472d8d330c713cb0e9127f749a16fb998e0ff18 100644
--- a/caisar.opam
+++ b/caisar.opam
@@ -3,7 +3,7 @@ opam-version: "2.0"
 version: "0.1"
 synopsis: "Framework for neural network verification"
 depends: [
-  "ocaml" {>= "4.10"}
+  "ocaml" {>= "4.13.0"}
   "dune-site" {>= "2.9.0"}
   "piqi" {>= "0.7.6"}
   "piqilib" {>= "0.6.14"}
diff --git a/dune-project b/dune-project
index 1792e8746af599944bad3faf7cdf165f1dd89a40..e059691fc41a0b1493359e469096b799f58d0fe3 100644
--- a/dune-project
+++ b/dune-project
@@ -13,7 +13,7 @@
   (name caisar)
   (synopsis "Framework for neural network verification")
   (depends
-   (ocaml (>= 4.10))
+   (ocaml (>= 4.13.0))
    (dune-site (>= 2.9.0))
    (piqi (>= 0.7.6))
    (piqilib (>= 0.6.14))
diff --git a/src/main.ml b/src/main.ml
index 9a9b01a8bf3bbd410846a66dfcccf4127ddc394d..bc097c4ed001ee8cfdf86707ce1dbe6101996d74 100644
--- a/src/main.ml
+++ b/src/main.ml
@@ -127,7 +127,7 @@ let verify_cmd =
   in
   let loadpath =
     let doc = "Additional loadpath." in
-    Arg.(value & opt_all string [] & info [ "L" ] ~doc)
+    Arg.(value & opt_all string [ "." ] & info [ "L"; "loadpath" ] ~doc)
   in
   let memlimit =
     let doc = "Memory limit (in megabytes)." in
diff --git a/src/verification.ml b/src/verification.ml
index ee4d1ded5ab445aa8c960bf672bc03b03897367c..8a6539c13aa7eb2e28958a18821ee5eb7df11705 100644
--- a/src/verification.ml
+++ b/src/verification.ml
@@ -54,8 +54,8 @@ let call_prover ~limit config (prover : Why3.Whyconf.config_prover) driver task
     | Some _ -> assert false (* By construction of the meta. *)
     | None -> invalid_arg (Fmt.str "No neural network model found in task")
   in
-  let nn_file = Filename.concat (Caml.Sys.getcwd ()) nn_file in
-  let command = Re.replace_string nnet_or_onnx ~by:nn_file command in
+  let nn_file = Unix.realpath nn_file in
+  let command = Re__Core.replace_string nnet_or_onnx ~by:nn_file command in
   let call_prover_on_task task_prepared =
     let prover_call =
       Driver.prove_task_prepared ~libdir:(Whyconf.libdir config)