diff --git a/CHANGELOG.md b/CHANGELOG.md
index 688d6512..fec8ec08 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,10 @@ and this project adheres to
 
 ## [unreleased]
 
+### Fixed
+
+- Always install dune within every extends.
+
 ## [3.0.2]
 
 ### Fixed
diff --git a/analysis/dist/index.js b/analysis/dist/index.js
index a6a969e9..f9b2cac1 100644
--- a/analysis/dist/index.js
+++ b/analysis/dist/index.js
@@ -34996,6 +34996,11 @@ async function installOpamPackages() {
         ]);
     });
 }
+async function installDune() {
+    await core.group("Install dune", async () => {
+        await (0,exec.exec)("opam", ["install", "dune"]);
+    });
+}
 
 ;// CONCATENATED MODULE: ./src/index.ts
 
@@ -35005,6 +35010,7 @@ async function installOpamPackages() {
 async function run() {
     try {
         await installOpamPackages();
+        await installDune();
         await analysis();
         external_node_process_namespaceObject.exit(0);
     }
diff --git a/lint-fmt/dist/index.js b/lint-fmt/dist/index.js
index 0c07f72b..7045938b 100644
--- a/lint-fmt/dist/index.js
+++ b/lint-fmt/dist/index.js
@@ -27978,6 +27978,11 @@ async function installOcamlformat(version) {
         await (0,exec.exec)("opam", ["install", `ocamlformat=${version}`]);
     });
 }
+async function installDune() {
+    await core.group("Install dune", async () => {
+        await (0,exec.exec)("opam", ["install", "dune"]);
+    });
+}
 
 ;// CONCATENATED MODULE: ./src/index.ts
 
@@ -27991,6 +27996,7 @@ async function run() {
         if (version) {
             await installOcamlformat(version);
         }
+        await installDune();
         await checkFmt();
         external_node_process_namespaceObject.exit(0);
     }
diff --git a/packages/analysis/src/index.ts b/packages/analysis/src/index.ts
index 454b5881..583398a6 100644
--- a/packages/analysis/src/index.ts
+++ b/packages/analysis/src/index.ts
@@ -1,11 +1,12 @@
 import * as process from "node:process";
 import * as core from "@actions/core";
 import { analysis } from "./analysis.js";
-import { installOpamPackages } from "./opam.js";
+import { installDune, installOpamPackages } from "./opam.js";
 
 async function run() {
   try {
     await installOpamPackages();
+    await installDune();
     await analysis();
     process.exit(0);
   } catch (error) {
diff --git a/packages/analysis/src/opam.ts b/packages/analysis/src/opam.ts
index 1847b994..e2fd60be 100644
--- a/packages/analysis/src/opam.ts
+++ b/packages/analysis/src/opam.ts
@@ -14,3 +14,9 @@ export async function installOpamPackages() {
     ]);
   });
 }
+
+export async function installDune() {
+  await core.group("Install dune", async () => {
+    await exec("opam", ["install", "dune"]);
+  });
+}
diff --git a/packages/lint-fmt/src/index.ts b/packages/lint-fmt/src/index.ts
index 5b489596..aa84f51b 100644
--- a/packages/lint-fmt/src/index.ts
+++ b/packages/lint-fmt/src/index.ts
@@ -2,7 +2,7 @@ import * as process from "node:process";
 import * as core from "@actions/core";
 import { checkFmt } from "./lint.js";
 import { getOcamlformatVersion } from "./ocamlformat.js";
-import { installOcamlformat } from "./opam.js";
+import { installDune, installOcamlformat } from "./opam.js";
 
 async function run() {
   try {
@@ -10,6 +10,7 @@ async function run() {
     if (version) {
       await installOcamlformat(version);
     }
+    await installDune();
     await checkFmt();
     process.exit(0);
   } catch (error) {
diff --git a/packages/lint-fmt/src/opam.ts b/packages/lint-fmt/src/opam.ts
index a4e043a1..f6a507e2 100644
--- a/packages/lint-fmt/src/opam.ts
+++ b/packages/lint-fmt/src/opam.ts
@@ -6,3 +6,9 @@ export async function installOcamlformat(version: string) {
     await exec("opam", ["install", `ocamlformat=${version}`]);
   });
 }
+
+export async function installDune() {
+  await core.group("Install dune", async () => {
+    await exec("opam", ["install", "dune"]);
+  });
+}