diff --git a/__test__/input-helper.test.ts b/__test__/input-helper.test.ts
index ecd3cd1cc..778c6ebc3 100644
--- a/__test__/input-helper.test.ts
+++ b/__test__/input-helper.test.ts
@@ -75,6 +75,20 @@ describe('input-helper tests', () => {
     expect(settings.repositoryPath).toBe(gitHubWorkspace)
   })
 
+  it('qualifies ref', () => {
+    let originalContext = mockGitHub.context
+    try {
+      mockGitHub.context = {...originalContext} // Shallow clone
+      mockGitHub.context.ref = 'some-unqualified-ref'
+      const settings: ISourceSettings = inputHelper.getInputs()
+      expect(settings).toBeTruthy()
+      expect(settings.commit).toBe('1234567890123456789012345678901234567890')
+      expect(settings.ref).toBe('refs/heads/some-unqualified-ref')
+    } finally {
+      mockGitHub.context = originalContext
+    }
+  })
+
   it('requires qualified repo', () => {
     inputs.repository = 'some-unqualified-repo'
     assert.throws(() => {
diff --git a/dist/index.js b/dist/index.js
index 19191939c..c58ef35e3 100644
--- a/dist/index.js
+++ b/dist/index.js
@@ -12757,6 +12757,11 @@ function getInputs() {
         if (isWorkflowRepository) {
             result.ref = github.context.ref;
             result.commit = github.context.sha;
+            // Some events have an unqualifed ref. For example when a PR is merged (pull_request closed event),
+            // the ref is unqualifed like "master" instead of "refs/heads/master".
+            if (result.commit && result.ref && !result.ref.startsWith('refs/')) {
+                result.ref = `refs/heads/${result.ref}`;
+            }
         }
         if (!result.ref && !result.commit) {
             result.ref = 'refs/heads/master';
diff --git a/src/input-helper.ts b/src/input-helper.ts
index 56b58f2ab..54339dab8 100644
--- a/src/input-helper.ts
+++ b/src/input-helper.ts
@@ -61,6 +61,12 @@ export function getInputs(): ISourceSettings {
     if (isWorkflowRepository) {
       result.ref = github.context.ref
       result.commit = github.context.sha
+
+      // Some events have an unqualifed ref. For example when a PR is merged (pull_request closed event),
+      // the ref is unqualifed like "master" instead of "refs/heads/master".
+      if (result.commit && result.ref && !result.ref.startsWith('refs/')) {
+        result.ref = `refs/heads/${result.ref}`
+      }
     }
 
     if (!result.ref && !result.commit) {