diff --git a/src/set-tokens.ts b/src/set-tokens.ts
index bbb397f..97a36dd 100644
--- a/src/set-tokens.ts
+++ b/src/set-tokens.ts
@@ -70,6 +70,10 @@ export function setGithubToken(
   core.debug(`eventName: ${eventName}`);
   let isProhibitedBranch = false;
 
+  if (externalRepository) {
+    throw new Error('GITHUB_TOKEN does not support to push to an external repository');
+  }
+
   if (eventName === 'push') {
     isProhibitedBranch = ref.includes(`refs/heads/${publishBranch}`);
     if (isProhibitedBranch) {
@@ -77,10 +81,6 @@ export function setGithubToken(
     }
   }
 
-  if (externalRepository) {
-    throw new Error('GITHUB_TOKEN does not support to push to an external repository');
-  }
-
   return `https://x-access-token:${githubToken}@github.com/${publishRepo}.git`;
 }