diff --git a/index.js b/index.js
index abca913..3b9ceea 100644
--- a/index.js
+++ b/index.js
@@ -142,13 +142,14 @@ const workspace = process.env.GITHUB_WORKSPACE;
       `"${process.env.GITHUB_EMAIL || 'gh-action-bump-version@users.noreply.github.com'}"`,
     ]);
 
-    const refsRegExResult = /refs\/[a-zA-Z]+\/(.*)/.exec(process.env.GITHUB_REF);
-    let currentBranch = refsRegExResult ? refsRegExResult[1] : undefined;
+    let currentBranch;
     let isPullRequest = false;
     if (process.env.GITHUB_HEAD_REF) {
       // Comes from a pull request
       currentBranch = process.env.GITHUB_HEAD_REF;
       isPullRequest = true;
+    } else {
+      currentBranch = /refs\/[a-zA-Z]+\/(.*)/.exec(process.env.GITHUB_REF)[1];
     }
     if (process.env['INPUT_TARGET-BRANCH']) {
       // We want to override the branch that we are pulling / pushing to