diff --git a/CHANGELOG.md b/CHANGELOG.md
index ff1b16f8..d18957f1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,10 @@ and this project adheres to
 
 ## [unreleased]
 
+### Fixed
+
+- Add an entry to the registry once the Cygwin cache is restored.
+
 ## [3.0.0-alpha]
 
 ### Added
diff --git a/dist/index.js b/dist/index.js
index 768cabf4..68f9b4b5 100644
--- a/dist/index.js
+++ b/dist/index.js
@@ -109532,6 +109532,7 @@ const { root: esm_root } = static_namespaceObject;
 
 
 
+
 function createHttpClient() {
     return new lib.HttpClient("OCamlBot (+https://github.com/ocaml/setup-ocaml)", [], { allowRetries: true, maxRetries: 5 });
 }
@@ -109586,6 +109587,23 @@ async function setupCygwin() {
         await io.cp(setup, CYGWIN_ROOT);
     });
 }
+async function addCygwinReg() {
+    const keyname = external_node_path_namespaceObject.join("HKLM", "SOFTWARE", "Cygwin", "setup");
+    const valuename = "rootdir";
+    const datatype = "REG_SZ";
+    const data = CYGWIN_ROOT;
+    await (0,lib_exec.exec)("reg", [
+        "add",
+        keyname,
+        "/v",
+        valuename,
+        "/t",
+        datatype,
+        "/d",
+        data,
+        "/f",
+    ]);
+}
 
 ;// CONCATENATED MODULE: ./src/cache.ts
 
@@ -109704,6 +109722,9 @@ async function restoreCygwinCache() {
     const { key, restoreKeys } = await composeCygwinCacheKeys();
     const paths = composeCygwinCachePaths();
     const cacheKey = await restoreCache(key, restoreKeys, paths);
+    if (cacheKey) {
+        await addCygwinReg();
+    }
     return cacheKey;
 }
 async function restoreOpamCache() {
diff --git a/dist/post/index.js b/dist/post/index.js
index 95b63493..c504c59c 100644
--- a/dist/post/index.js
+++ b/dist/post/index.js
@@ -84916,6 +84916,9 @@ async function restoreCygwinCache() {
     const { key, restoreKeys } = await composeCygwinCacheKeys();
     const paths = composeCygwinCachePaths();
     const cacheKey = await restoreCache(key, restoreKeys, paths);
+    if (cacheKey) {
+        await addCygwinReg();
+    }
     return cacheKey;
 }
 async function restoreOpamCache() {
diff --git a/packages/setup-ocaml/src/cache.ts b/packages/setup-ocaml/src/cache.ts
index 463b3565..3dcda382 100644
--- a/packages/setup-ocaml/src/cache.ts
+++ b/packages/setup-ocaml/src/cache.ts
@@ -18,7 +18,7 @@ import {
 } from "./constants.js";
 import { getLatestOpamRelease } from "./opam.js";
 import { resolveCompiler } from "./version.js";
-import { getCygwinVersion } from "./windows.js";
+import { addCygwinReg, getCygwinVersion } from "./windows.js";
 
 async function composeCygwinCacheKeys() {
   const cygwinVersion = await getCygwinVersion();
@@ -151,6 +151,9 @@ async function restoreCygwinCache() {
   const { key, restoreKeys } = await composeCygwinCacheKeys();
   const paths = composeCygwinCachePaths();
   const cacheKey = await restoreCache(key, restoreKeys, paths);
+  if (cacheKey) {
+    await addCygwinReg();
+  }
   return cacheKey;
 }
 
diff --git a/packages/setup-ocaml/src/windows.ts b/packages/setup-ocaml/src/windows.ts
index 666f20c3..e20965b3 100644
--- a/packages/setup-ocaml/src/windows.ts
+++ b/packages/setup-ocaml/src/windows.ts
@@ -1,3 +1,4 @@
+import * as path from "node:path";
 import * as core from "@actions/core";
 import { exec } from "@actions/exec";
 import { HttpClient } from "@actions/http-client";
@@ -74,3 +75,21 @@ export async function setupCygwin() {
     await io.cp(setup, CYGWIN_ROOT);
   });
 }
+
+export async function addCygwinReg() {
+  const keyname = path.join("HKLM", "SOFTWARE", "Cygwin", "setup");
+  const valuename = "rootdir";
+  const datatype = "REG_SZ";
+  const data = CYGWIN_ROOT;
+  await exec("reg", [
+    "add",
+    keyname,
+    "/v",
+    valuename,
+    "/t",
+    datatype,
+    "/d",
+    data,
+    "/f",
+  ]);
+}