diff --git a/__tests__/installer.test.ts b/__tests__/installer.test.ts
index 59fc9798..99489236 100644
--- a/__tests__/installer.test.ts
+++ b/__tests__/installer.test.ts
@@ -696,7 +696,7 @@ describe('setup-node', () => {
       );
     });
 
-    it('fail with unexpected LTS alias (lts/)', async () => {
+    it('fail with unable to parse LTS alias (lts/)', async () => {
       // arrange
       inputs['node-version'] = 'lts/';
 
@@ -713,7 +713,7 @@ describe('setup-node', () => {
         'Getting manifest from actions/node-versions@main'
       );
       expect(cnSpy).toHaveBeenCalledWith(
-        `::error::Unexpected LTS alias '' for Node version 'lts/'${osm.EOL}`
+        `::error::Unable to parse LTS alias for Node version 'lts/'${osm.EOL}`
       );
     });
 
diff --git a/dist/index.js b/dist/index.js
index 170f8279..1c614cd8 100644
--- a/dist/index.js
+++ b/dist/index.js
@@ -13225,7 +13225,7 @@ function getNode(versionSpec, stable, checkLatest, auth, arch = os.arch()) {
 }
 exports.getNode = getNode;
 function isLtsAlias(versionSpec) {
-    return versionSpec.startsWith('lts');
+    return versionSpec.startsWith('lts/');
 }
 function getManifest(auth) {
     core.debug('Getting manifest from actions/node-versions@main');
@@ -13235,7 +13235,7 @@ function resolveLtsAliasFromManifest(versionSpec, stable, manifest) {
     var _a;
     const alias = (_a = versionSpec.split('lts/')[1]) === null || _a === void 0 ? void 0 : _a.toLowerCase();
     if (!alias) {
-        throw new Error(`Unexpected LTS alias '${alias}' for Node version '${versionSpec}'`);
+        throw new Error(`Unable to parse LTS alias for Node version '${versionSpec}'`);
     }
     core.debug(`LTS alias '${alias}' for Node version '${versionSpec}'`);
     // Supported formats are `lts/<alias>` and `lts/*`. Where asterisk means highest possible LTS.
diff --git a/src/installer.ts b/src/installer.ts
index 47d24c93..b43e5448 100644
--- a/src/installer.ts
+++ b/src/installer.ts
@@ -193,7 +193,7 @@ export async function getNode(
 }
 
 function isLtsAlias(versionSpec: string): boolean {
-  return versionSpec.startsWith('lts');
+  return versionSpec.startsWith('lts/');
 }
 
 function getManifest(auth: string | undefined): Promise<tc.IToolRelease[]> {
@@ -210,7 +210,7 @@ function resolveLtsAliasFromManifest(
 
   if (!alias) {
     throw new Error(
-      `Unexpected LTS alias '${alias}' for Node version '${versionSpec}'`
+      `Unable to parse LTS alias for Node version '${versionSpec}'`
     );
   }