diff --git a/.github/workflows/gh-pages.yml b/.github/workflows/gh-pages.yml
index 64284fcee..525870f69 100644
--- a/.github/workflows/gh-pages.yml
+++ b/.github/workflows/gh-pages.yml
@@ -20,7 +20,6 @@ jobs:
           allow-prerelease-opam: true
 
       # Until there's a new release of `trace`, we need to pin it.
-      - run: opam pin https://github.com/c-cube/ocaml-trace.git#HEAD -y -n
       - run: opam pin . -y -n
       - run: opam install odig imandrakit imandrakit-thread imandrakit-io imandrakit-log
       - run: opam exec -- odig odoc --cache-dir=_doc/ imandrakit imandrakit-thread imandrakit-io imandrakit-log
diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 3a5913920..ddeb19d88 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -1,4 +1,4 @@
-name: Build and Test
+name: Imandrakit CI
 
 on:
   push:
@@ -7,40 +7,8 @@ on:
   pull_request:
 
 jobs:
-  build-all-versions:
-    name: build
-    timeout-minutes: 15
-    strategy:
-      fail-fast: true
-      matrix:
-        os:
-            - ubuntu-latest
-              #- macos-latest
-              #- windows-latest
-        ocaml-compiler:
-            - '4.14'
-
-    runs-on: ${{ matrix.os }}
-    steps:
-      - uses: actions/checkout@main
-      - name: Use OCaml ${{ matrix.ocaml-compiler }}
-        uses: ocaml/setup-ocaml@v3
-        with:
-          ocaml-compiler: ${{ matrix.ocaml-compiler }}
-          dune-cache: true
-          allow-prerelease-opam: true
-
-      - run: opam pin trace --dev -y -n; opam pin trace-tef --dev -y -n
-      - run: opam install -t imandrakit imandrakit-log imandrakit-io --deps-only
-      - run: opam exec -- dune build @install -p imandrakit,imandrakit-log,imandrakit-io
-      - run: opam exec -- dune build @runtest -p imandrakit,imandrakit-log,imandrakit-io
-
-      # install some depopts and build+test again
-      - run: opam install camlzip
-      - run: opam exec -- dune build @install @runtest -p imandrakit,imandrakit-log,imandrakit-io
-
-  build-ocaml5:
-    name: build-ocaml5
+  build:
+    name: "Build & Test"
     timeout-minutes: 15
     strategy:
       fail-fast: true
@@ -52,6 +20,7 @@ jobs:
         ocaml-compiler:
             - '5.1'
             - '5.2'
+            - '5.3'
 
     runs-on: ${{ matrix.os }}
     steps:
@@ -63,7 +32,6 @@ jobs:
           dune-cache: true
           allow-prerelease-opam: true
 
-      - run: opam pin trace --dev -y -n; opam pin trace-tef --dev -y -n
       - run: opam install -t imandrakit imandrakit-log imandrakit-io imandrakit-thread --deps-only
       - run: opam exec -- dune build @install -p imandrakit,imandrakit-io,imandrakit-log,imandrakit-thread
       - run: opam exec -- dune build @runtest -p imandrakit,imandrakit-io,imandrakit-log,imandrakit-thread
diff --git a/src/leb128/stubs.c b/src/leb128/stubs.c
index b67097ff8..becf0ae49 100644
--- a/src/leb128/stubs.c
+++ b/src/leb128/stubs.c
@@ -58,14 +58,14 @@ static inline void ix_leb128_varint(unsigned char *str, uint64_t i) {
 
 // write `i` starting at `idx`
 CAMLprim value caml_ix_leb128_varint(value _str, intnat idx, int64_t i) {
-  char *str = Bytes_val(_str);
+  unsigned char *str = Bytes_val(_str);
   ix_leb128_varint(str + idx, i);
   return Val_unit;
 }
 
 CAMLprim value caml_ix_leb128_varint_byte(value _str, value _idx, value _i) {
   CAMLparam3(_str, _idx, _i);
-  char *str = Bytes_val(_str);
+  unsigned char *str = Bytes_val(_str);
   int idx = Int_val(_idx);
   int64_t i = Int64_val(_i);
   ix_leb128_varint(str + idx, i);
diff --git a/src/twine-utils/dune b/src/twine-utils/dune
index e26981f0a..de2ab258b 100644
--- a/src/twine-utils/dune
+++ b/src/twine-utils/dune
@@ -1,6 +1,7 @@
 (executable
  (name main)
- (modes (byte exe))
+ (modes
+  (byte exe))
  (public_name twine_utils)
  (package twine-utils)
  (preprocess