diff --git a/index.js b/index.js
index 7b04db9..4e17dda 100644
--- a/index.js
+++ b/index.js
@@ -19,7 +19,7 @@ async function getAndPostPullRequests() {
     const branch = core.getInput("branch");
     core.info(`The branch ${branch} should be merged.`);
 
-    const base_branch = core.getInput("base_branch");
+    const base_branch = core.getInput("base_branch") || "main";
     core.info(`The branch ${base_branch} should be merged into.`);
 
     // core.info(`Post Data: ${JSON.stringify(postData)}`);