diff --git a/__tests__/cacheTwirpClient.test.ts b/__tests__/cacheTwirpClient.test.ts
index dd38e8f..e981ce1 100644
--- a/__tests__/cacheTwirpClient.test.ts
+++ b/__tests__/cacheTwirpClient.test.ts
@@ -16,12 +16,12 @@ describe('CacheServiceClient', () => {
 
   beforeEach(() => {
     jest.clearAllMocks()
-    process.env['ACTIONS_RUNTIME_TOKEN'] = 'test-token' // <-- set the required env variable
+    process.env['ACTIONS_RUNTIME_TOKEN'] = 'test-token'
     client = new CacheServiceClient('test-agent')
   })
 
   afterEach(() => {
-    delete process.env['ACTIONS_RUNTIME_TOKEN'] // <-- clean up after tests
+    delete process.env['ACTIONS_RUNTIME_TOKEN']
   })
 
   describe('maskSecretUrls', () => {
@@ -36,7 +36,7 @@ describe('CacheServiceClient', () => {
 
       expect(setSecret).toHaveBeenCalledWith('secret-token')
       expect(debug).toHaveBeenCalledWith(
-        'Masked signedUploadUrl: https://example.com/upload?se=2025-03-05T16%3A47%3A23Z&sig=***'
+        'Masked signed_upload_url: https://example.com/upload?se=2025-03-05T16%3A47%3A23Z&sig=***'
       )
     })
 
@@ -52,7 +52,7 @@ describe('CacheServiceClient', () => {
 
       expect(setSecret).toHaveBeenCalledWith('secret-token')
       expect(debug).toHaveBeenCalledWith(
-        'Masked signedDownloadUrl: https://example.com/download?se=2025-03-05T16%3A47%3A23Z&sig=***'
+        'Masked signed_download_url: https://example.com/download?se=2025-03-05T16%3A47%3A23Z&sig=***'
       )
     })
 
@@ -75,7 +75,7 @@ describe('CacheServiceClient', () => {
 
       expect(setSecret).toHaveBeenCalledWith('secret-token')
       expect(debug).toHaveBeenCalledWith(
-        'Masked signedUploadUrl: https://example.com/upload?se=2025-03-05T16%3A47%3A23Z&sig=***'
+        'Masked signed_upload_url: https://example.com/upload?se=2025-03-05T16%3A47%3A23Z&sig=***'
       )
     })
 
@@ -91,7 +91,7 @@ describe('CacheServiceClient', () => {
 
       expect(setSecret).toHaveBeenCalledWith('secret-token')
       expect(debug).toHaveBeenCalledWith(
-        'Masked signedDownloadUrl: https://example.com/download?se=2025-03-05T16%3A47%3A23Z&sig=***'
+        'Masked signed_download_url: https://example.com/download?se=2025-03-05T16%3A47%3A23Z&sig=***'
       )
     })
   })
diff --git a/package.json b/package.json
index 3a200f8..4667849 100644
--- a/package.json
+++ b/package.json
@@ -31,7 +31,8 @@
   "scripts": {
     "audit-moderate": "npm install && npm audit --json --audit-level=moderate > audit.json",
     "test": "echo \"Error: run tests from root\" && exit 1",
-    "tsc": "tsc"
+    "tsc": "tsc",
+    "clean": "rm -rf node_modules lib"
   },
   "bugs": {
     "url": "https://github.com/actions/toolkit/issues"
@@ -46,6 +47,7 @@
     "@azure/ms-rest-js": "^2.6.0",
     "@azure/storage-blob": "^12.13.0",
     "@protobuf-ts/plugin": "^2.9.4",
+    "@types/node": "^22.13.9",
     "semver": "^6.3.1"
   },
   "devDependencies": {
diff --git a/src/internal/shared/cacheTwirpClient.ts b/src/internal/shared/cacheTwirpClient.ts
index 9c12112..2c8acbe 100644
--- a/src/internal/shared/cacheTwirpClient.ts
+++ b/src/internal/shared/cacheTwirpClient.ts
@@ -1,4 +1,4 @@
-import {info, debug, maskSigUrl} from '@actions/core'
+import {info, debug, setSecret} from '@actions/core'
 import {getUserAgentString} from './user-agent'
 import {NetworkError, UsageError} from './errors'
 import {getCacheServiceURL} from '../config'
@@ -153,14 +153,27 @@ export class CacheServiceClient implements Rpc {
     throw new Error(`Request failed`)
   }
 
+  /**
+   * Masks the `sig` parameter in a URL and sets it as a secret.
+   * @param url The URL containing the `sig` parameter.
+   * @param urlType The type of the URL (e.g., 'signed_upload_url', 'signed_download_url').
+   */
+  maskSigUrl(url: string, urlType: string): void {
+    const sigMatch = url.match(/[?&]sig=([^&]+)/)
+    if (sigMatch) {
+      setSecret(sigMatch[1])
+      debug(`Masked ${urlType}: ${url.replace(sigMatch[1], '***')}`)
+    }
+  }
+
   maskSecretUrls(
     body: CreateCacheEntryResponse | GetCacheEntryDownloadURLResponse
   ): void {
     if ('signedUploadUrl' in body && body.signedUploadUrl) {
-      maskSigUrl(body.signedUploadUrl, 'signedUploadUrl')
+      this.maskSigUrl(body.signedUploadUrl, 'signed_upload_url')
     }
     if ('signedDownloadUrl' in body && body.signedDownloadUrl) {
-      maskSigUrl(body.signedDownloadUrl, 'signedDownloadUrl')
+      this.maskSigUrl(body.signedDownloadUrl, 'signed_download_url')
     }
   }