diff --git a/packages/crx-monkey/src/node/config.ts b/packages/crx-monkey/src/node/config.ts
index c8d740e..cc70cbb 100644
--- a/packages/crx-monkey/src/node/config.ts
+++ b/packages/crx-monkey/src/node/config.ts
@@ -63,12 +63,13 @@ async function search(dir: string): Promise<string | null> {
 }
 
 function isKeyof<T>(obj: object, key: T | string): key is T {
-  Object.entries(obj).forEach(([objkey]) => {
+  let result = false;
+  Object.keys(obj).forEach((objkey) => {
     if (key === objkey) {
-      return true;
+      result = true;
     }
   });
-  return false;
+  return result;
 }
 
 function setDefaultConfig(config: Record<string, never>) {
diff --git a/packages/crx-monkey/src/node/handlers/dev/server/scriptHostingServer.ts b/packages/crx-monkey/src/node/handlers/dev/server/scriptHostingServer.ts
index 2b4f18e..eae23f8 100644
--- a/packages/crx-monkey/src/node/handlers/dev/server/scriptHostingServer.ts
+++ b/packages/crx-monkey/src/node/handlers/dev/server/scriptHostingServer.ts
@@ -1,6 +1,7 @@
 import express from 'express';
 import { getConfig } from 'src/node/config';
 import path from 'path';
+import fse from 'fs-extra';
 
 export class ScriptHostingServer {
   private readonly app: express.Express;
@@ -30,17 +31,24 @@ export class ScriptHostingServer {
     });
 
     this.app.get('/userscript', (req, res) => {
-      if (config.userscriptOutput !== undefined) {
-        res.sendFile(config.userscriptOutput);
+      const filepath = path.join(path.dirname(config.manifestJsonPath), config.userscriptOutput);
+
+      if (fse.existsSync(filepath)) {
+        res.sendFile(filepath);
       } else {
         res.send(400);
       }
     });
 
     this.app.get('/dev.user.js', (req, res) => {
-      if (config.userscriptOutput !== undefined) {
-        const userscriptDir = path.dirname(config.userscriptOutput);
-        res.sendFile(path.join(userscriptDir, 'crx-monkey-dev.user.js'));
+      const filepath = path.join(
+        path.dirname(config.manifestJsonPath),
+        path.dirname(config.userscriptOutput),
+        'crx-monkey-dev.user.js',
+      );
+
+      if (fse.existsSync(filepath)) {
+        res.sendFile(filepath);
       } else {
         res.send(400);
       }
diff --git a/packages/crx-monkey/src/node/handlers/utils.ts b/packages/crx-monkey/src/node/handlers/utils.ts
index 2f4a11e..1f820a8 100644
--- a/packages/crx-monkey/src/node/handlers/utils.ts
+++ b/packages/crx-monkey/src/node/handlers/utils.ts
@@ -25,13 +25,8 @@ export function getlocalesPath() {
 
 export function copyPublic() {
   const config = getConfig();
-  const publicDir = config.publicDir;
-
-  if (
-    publicDir !== undefined &&
-    fse.pathExistsSync(publicDir) &&
-    config.chromeOutputDir !== undefined
-  ) {
+  const publicDir = path.join(process.cwd(), config.publicDir);
+  if (publicDir !== undefined && fse.pathExistsSync(publicDir)) {
     fse.copy(publicDir, path.join(config.chromeOutputDir, path.basename(publicDir)));
   }
 }