diff --git a/packages/next/src/build/analysis/get-page-static-info.ts b/packages/next/src/build/analysis/get-page-static-info.ts
index 6d6cc421f895..ec08c72f4a6c 100644
--- a/packages/next/src/build/analysis/get-page-static-info.ts
+++ b/packages/next/src/build/analysis/get-page-static-info.ts
@@ -286,8 +286,9 @@ async function tryToReadFile(filePath: string, shouldThrow: boolean) {
     return await fs.readFile(filePath, {
       encoding: 'utf8',
     })
-  } catch (error) {
+  } catch (error: any) {
     if (shouldThrow) {
+      error.message = `Next.js ERROR: Failed to read file ${filePath}:\n${error.message}`
       throw error
     }
   }
diff --git a/packages/next/src/build/index.ts b/packages/next/src/build/index.ts
index c0fde0830c4c..a86398b9d565 100644
--- a/packages/next/src/build/index.ts
+++ b/packages/next/src/build/index.ts
@@ -2865,7 +2865,6 @@ export default async function build(
 
           // If there's /not-found inside app, we prefer it over the pages 404
           if (hasStaticApp404) {
-            // await moveExportedPage('/_error', '/404', '/404', false, 'html')
             await moveExportedAppNotFoundTo404()
           } else {
             // Only move /404 to /404 when there is no custom 404 as in that case we don't know about the 404 page
diff --git a/packages/next/src/server/lib/find-page-file.ts b/packages/next/src/server/lib/find-page-file.ts
index b3d01383b68d..155462775ba9 100644
--- a/packages/next/src/server/lib/find-page-file.ts
+++ b/packages/next/src/server/lib/find-page-file.ts
@@ -91,7 +91,7 @@ export function createValidFileMatcher(
       pageExtensions
     )}$`
   )
-  const leafOnlyNotFoundFileRegex = new RegExp(
+  const rootNotFoundFileRegex = new RegExp(
     `^not-found\\.${getExtensionRegexString(pageExtensions)}$`
   )
   /** TODO-METADATA: support other metadata routes
@@ -136,7 +136,7 @@ export function createValidFileMatcher(
       return false
     }
     const rest = filePath.slice(appDirPath.length + 1)
-    return leafOnlyNotFoundFileRegex.test(rest)
+    return rootNotFoundFileRegex.test(rest)
   }
 
   return {