diff --git a/remark-modified-time.mjs b/remark-modified-time.mjs
index 7291612..8b93e00 100644
--- a/remark-modified-time.mjs
+++ b/remark-modified-time.mjs
@@ -3,7 +3,7 @@ import { execSync } from "node:child_process";
 export function remarkModifiedTime() {
   return (tree, file) => {
     const filepath = file.history[0];
-    const result = import.meta.env.PUBLIC_COMMIT === "" ? "Unavailable" : execSync(`git log -1 --pretty="format:%cI" "${filepath}"`);
+    const result = typeof import.meta.env.PUBLIC_COMMIT === "undefined" ? "Unavailable" : execSync(`git log -1 --pretty="format:%cI" "${filepath}"`);
     file.data.astro.frontmatter.lastModified = result.toString();
   };
 }
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