diff --git a/action.yml b/action.yml
index 4f0655b..53f0a0d 100644
--- a/action.yml
+++ b/action.yml
@@ -10,7 +10,7 @@ inputs:
   base-ref:
     description: 'Base ref to compare against (defaults to main or PR target)'
     required: true
-    default: 'main'
+    default: 'origin/main'
   github-token:
     description: 'The GitHub token for authentication.'
     required: true
diff --git a/main.js b/main.js
index 1ea28c8..3e3fbcf 100644
--- a/main.js
+++ b/main.js
@@ -1,9 +1,7 @@
-
-      import { fileURLToPath } from 'node:url';
+import { fileURLToPath } from 'node:url';
       import { createRequire as topLevelCreateRequire } from 'node:module';
       import { dirname as topLevelDirname } from 'path';
       const require = topLevelCreateRequire(import.meta.url);
-    
 var __create = Object.create;
 var __defProp = Object.defineProperty;
 var __getOwnPropDesc = Object.getOwnPropertyDescriptor;
diff --git a/src/git.ts b/src/git.ts
index 48a934e..4d4c63f 100644
--- a/src/git.ts
+++ b/src/git.ts
@@ -23,7 +23,7 @@ export function getFileFromRef(
 export function getBaseRef(): string {
   const inputBaseRef = core.getInput('base-ref');
   if (inputBaseRef) {
-    return inputBaseRef;
+    return inputBaseRef.includes('/') ? inputBaseRef : `origin/${inputBaseRef}`;
   }
 
   const githubBaseRef = github.context.payload.pull_request?.base.ref;
diff --git a/test/git_test.ts b/test/git_test.ts
index d1f6290..415c064 100644
--- a/test/git_test.ts
+++ b/test/git_test.ts
@@ -1,19 +1,29 @@
 import {describe, it, expect, beforeEach, vi} from 'vitest';
 import * as git from '../src/git.js';
 import * as github from '@actions/github';
-import process from 'process';
+import * as process from 'process';
 import {fileURLToPath} from 'node:url';
-import path from 'node:path';
+import * as path from 'node:path';
 
 const currentDir = path.dirname(fileURLToPath(import.meta.url));
 const rootDir = path.join(currentDir, '..');
 
 describe('getBaseRef', () => {
   it('should return input base ref if provided', () => {
+    try {
+      process.env['INPUT_BASE-REF'] = 'origin/feature-branch';
+      const baseRef = git.getBaseRef();
+      expect(baseRef).toBe('origin/feature-branch');
+    } finally {
+      delete process.env['INPUT_BASE-REF'];
+    }
+  });
+
+  it('should prepend origin if not set', () => {
     try {
       process.env['INPUT_BASE-REF'] = 'feature-branch';
       const baseRef = git.getBaseRef();
-      expect(baseRef).toBe('feature-branch');
+      expect(baseRef).toBe('origin/feature-branch');
     } finally {
       delete process.env['INPUT_BASE-REF'];
     }