diff --git a/lib/remark/last-modified.ts b/lib/remark/last-modified.ts
index 6865219..73b4d72 100644
--- a/lib/remark/last-modified.ts
+++ b/lib/remark/last-modified.ts
@@ -5,17 +5,28 @@ import { resolve } from 'path'
 
 function remarkModifiedTime() {
   return function (tree, file) {
+    console.log('tree:', tree)
+    console.log('file:', file)
     const filepath = file.history[0]
+    console.log('filepath:', filepath)
+
+    if (!filepath) {
+      console.error('Error: filepath is undefined')
+      return
+    }
 
     try {
       // Resolve the absolute path of the file
       const absoluteFilePath = resolve(filepath)
+      console.log('absoluteFilePath:', absoluteFilePath)
 
       // Get the root directory of the repository
       const repoRoot = execSync('git rev-parse --show-toplevel').toString().trim()
+      console.log('repoRoot:', repoRoot)
 
       // Get the relative path of the file from the repository root
       const relativeFilePath = absoluteFilePath.replace(`${repoRoot}/`, '')
+      console.log('relativeFilePath:', relativeFilePath)
 
       // Check if the file is within a submodule
       const submodulePath = execSync(`git submodule foreach --quiet 'echo $path'`)
@@ -23,6 +34,7 @@ function remarkModifiedTime() {
         .trim()
         .split('\n')
         .find(submodule => relativeFilePath.startsWith(submodule))
+      console.log('submodulePath:', submodulePath)
 
       let result
       if (submodulePath) {
@@ -40,6 +52,7 @@ function remarkModifiedTime() {
       }
 
       file.data.astro.frontmatter.lastModified = result
+      console.log('lastModified:', result)
     } catch (error) {
       console.error('Error getting last modified time:', error)
     }