diff --git a/.github/workflows/build-and-test.yml b/.github/workflows/build-and-test.yml
index 689eee755..61b15b91e 100644
--- a/.github/workflows/build-and-test.yml
+++ b/.github/workflows/build-and-test.yml
@@ -45,11 +45,11 @@ jobs:
       - name: Set-up OCaml
         uses: ocaml/setup-ocaml@v3
         with:
-          ocaml-compiler: "5.2"
+          ocaml-compiler: "ocaml-base-compiler.5.3.0"
 
       # Remove this pin once a compatible version of Merlin has been released
-      # - name: Pin dev Merlin
-      #   run: opam pin https://github.com/ocaml/merlin.git#main
+      - name: Pin dev Merlin
+        run: opam --cli=2.1 pin --with-version=5.4-503 https://github.com/ocaml/merlin.git#main
 
       - name: Build and install dependencies
         run: opam install .
@@ -81,13 +81,17 @@ jobs:
       - name: Set-up OCaml
         uses: ocaml/setup-ocaml@v3
         with:
-          ocaml-compiler: "5.2"
+          ocaml-compiler: "ocaml-base-compiler.5.3.0"
 
       - name: Set git user
         run: |
           git config --global user.name github-actions[bot]
           git config --global user.email github-actions[bot]@users.noreply.github.com
 
+      # Remove this pin once a compatible version of Merlin has been released
+      - name: Pin dev Merlin
+        run: opam --cli=2.1 pin --with-version=5.4-503 https://github.com/ocaml/merlin.git#main
+
       - name: Install dependencies
         run: |
           opam install . --deps-only
diff --git a/CHANGES.md b/CHANGES.md
index e1749bd08..77c5c2f37 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -22,6 +22,7 @@
   [`ocamllsp/typeSearch`](/ocaml-lsp-server/docs/ocamllsp/typeSearch-spec.md) request (#1369)
 
 - Make MerlinJump code action configurable (#1376)
+- Add support for OCaml 5.3 (#1386)
 
 - Add custom [`ocamllsp/jump`](/ocaml-lsp-server/docs/ocamllsp/merlinJump-spec.md) request (#1374)
 
diff --git a/dune-project b/dune-project
index a583cd964..8c1d67e8e 100644
--- a/dune-project
+++ b/dune-project
@@ -56,7 +56,7 @@ possible and does not make any assumptions about IO.
   dyn
   stdune
   (fiber (and (>= 3.1.1) (< 4.0.0)))
-  (ocaml (and (>= 5.2.0) (< 5.3)))
+  (ocaml (and (>= 5.3) (< 5.4)))
   xdg
   ordering
   dune-build-info
@@ -70,7 +70,7 @@ possible and does not make any assumptions about IO.
   (csexp (>= 1.5))
   (ocamlformat-rpc-lib (>= 0.21.0))
   (odoc :with-doc)
-  (merlin-lib (and (>= 5.2) (< 6.0)))
+  (merlin-lib (and (>= 5.4) (< 6.0)))
   (ppx_yojson_conv :with-dev-setup)))
 
 (package
diff --git a/ocaml-lsp-server.opam b/ocaml-lsp-server.opam
index bf21a7132..ac47b51b7 100644
--- a/ocaml-lsp-server.opam
+++ b/ocaml-lsp-server.opam
@@ -31,7 +31,7 @@ depends: [
   "dyn"
   "stdune"
   "fiber" {>= "3.1.1" & < "4.0.0"}
-  "ocaml" {>= "5.2.0" & < "5.3"}
+  "ocaml" {>= "5.3" & < "5.4"}
   "xdg"
   "ordering"
   "dune-build-info"
@@ -45,7 +45,7 @@ depends: [
   "csexp" {>= "1.5"}
   "ocamlformat-rpc-lib" {>= "0.21.0"}
   "odoc" {with-doc}
-  "merlin-lib" {>= "5.2" & < "6.0"}
+  "merlin-lib" {>= "5.4" & < "6.0"}
   "ppx_yojson_conv" {with-dev-setup}
 ]
 dev-repo: "git+https://github.com/ocaml/ocaml-lsp.git"
diff --git a/ocaml-lsp-server/src/code_actions/action_extract.ml b/ocaml-lsp-server/src/code_actions/action_extract.ml
index 00358f213..7946c50f4 100644
--- a/ocaml-lsp-server/src/code_actions/action_extract.ml
+++ b/ocaml-lsp-server/src/code_actions/action_extract.ml
@@ -1,6 +1,7 @@
 open Import
 open Option.O
 module H = Ocaml_parsing.Ast_helper
+module Typedtree_utils = Merlin_analysis.Typedtree_utils
 
 let range_contains_loc range loc =
   match Range.of_loc_opt loc with
@@ -75,8 +76,12 @@ let tightest_enclosing_binder_position typedtree range =
       | Texp_open (_, body) -> found_if_expr_contains body
       | Texp_letop { body; _ } -> found_if_case_contains [ body ]
       | Texp_function (_, Tfunction_cases { cases; _ }) -> found_if_case_contains cases
-      | Texp_match (_, cases, _) -> found_if_case_contains cases
-      | Texp_try (_, cases) -> found_if_case_contains cases
+      | Texp_match _ ->
+        let m = Typedtree_utils.texp_match_of_expr expr |> Option.value_exn in
+        found_if_case_contains m.computation_cases
+      | Texp_try _ ->
+        let t = Typedtree_utils.texp_try_of_expr expr |> Option.value_exn in
+        found_if_case_contains t.value_cases
       | _ -> ())
   in
   let structure_item_iter (iter : I.iterator) (item : Typedtree.structure_item) =
diff --git a/ocaml-lsp-server/src/folding_range.ml b/ocaml-lsp-server/src/folding_range.ml
index 68c00e6ac..089e41548 100644
--- a/ocaml-lsp-server/src/folding_range.ml
+++ b/ocaml-lsp-server/src/folding_range.ml
@@ -159,7 +159,8 @@ let fold_over_parsetree (parsetree : Mreader.parsetree) =
       | Ppat_exception _
       | Ppat_extension _
       | Ppat_open _
-      | Ppat_any -> Ast_iterator.default_iterator.pat self p
+      | Ppat_any
+      | _ -> Ast_iterator.default_iterator.pat self p
     in
     let expr (self : Ast_iterator.iterator) (expr : Parsetree.expression) =
       match expr.pexp_desc with
diff --git a/ocaml-lsp-server/src/semantic_highlighting.ml b/ocaml-lsp-server/src/semantic_highlighting.ml
index 9aaa4eb07..c48a34e9f 100644
--- a/ocaml-lsp-server/src/semantic_highlighting.ml
+++ b/ocaml-lsp-server/src/semantic_highlighting.ml
@@ -1,6 +1,7 @@
 open Import
 open Fiber.O
 module Array_view = Lsp.Private.Array_view
+module Parsetree_utils = Merlin_analysis.Parsetree_utils
 
 (* TODO:
 
@@ -508,7 +509,7 @@ end = struct
 
   let const loc (constant : Parsetree.constant) =
     let token_type =
-      match constant with
+      match Parsetree_utils.constant_desc constant with
       | Parsetree.Pconst_integer _ | Pconst_float _ -> Token_type.of_builtin Number
       | Pconst_char _ | Pconst_string _ -> Token_type.of_builtin String
     in
@@ -719,7 +720,8 @@ end = struct
       | Ppat_tuple _
       | Ppat_lazy _
       | Ppat_any
-      | Ppat_interval _ -> `Default_iterator
+      | Ppat_interval _
+      | _ -> `Default_iterator
     with
     | `Default_iterator -> Ast_iterator.default_iterator.pat self pat
     | `Custom_iterator -> self.attributes self ppat_attributes
diff --git a/ocaml-lsp-server/test/e2e/__tests__/textDocument-diagnostics.ts b/ocaml-lsp-server/test/e2e/__tests__/textDocument-diagnostics.ts
index 9c28eac96..248ffc898 100644
--- a/ocaml-lsp-server/test/e2e/__tests__/textDocument-diagnostics.ts
+++ b/ocaml-lsp-server/test/e2e/__tests__/textDocument-diagnostics.ts
@@ -410,7 +410,7 @@ The type int is not compatible with the type unit",
 {
   "diagnostics": [
     {
-      "message": "This expression has type unit but an expression was expected of type int",
+      "message": "The constructor () has type unit but an expression was expected of type int",
       "range": {
         "end": {
           "character": 42,
@@ -457,7 +457,7 @@ The type int is not compatible with the type unit",
       "source": "ocamllsp",
     },
     {
-      "message": "This expression has type string but an expression was expected of type int",
+      "message": "This constant has type string but an expression was expected of type int",
       "range": {
         "end": {
           "character": 9,