diff --git a/package.json b/package.json
index f049fe6..aff59f8 100644
--- a/package.json
+++ b/package.json
@@ -35,7 +35,7 @@
     "tslint": "^5.1.0"
   },
   "dependencies": {
-    "fs-p": "2.0.0",
+    "fs-extra": "^4.0.2",
     "globby": "^6.1.0",
     "lodash": "^4.17.4",
     "typescript": "^2.2.2"
diff --git a/src/index.ts b/src/index.ts
index 959f0d4..4d19d1a 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,5 +1,5 @@
 import * as path from 'path'
-import * as fs from 'fs-p'
+import * as fs from 'fs-extra'
 
 import * as _ from 'lodash'
 import * as globby from 'globby'
diff --git a/src/typescript.ts b/src/typescript.ts
index 1f07bdc..f18e59b 100644
--- a/src/typescript.ts
+++ b/src/typescript.ts
@@ -1,5 +1,5 @@
 import * as ts from 'typescript'
-import * as fs from 'fs-p'
+import * as fs from 'fs-extra'
 import * as _ from 'lodash'
 import { ServerlessFunction } from './types'
 import * as path from 'path'
diff --git a/src/watchFiles.ts b/src/watchFiles.ts
index eb4acb6..8b8322c 100644
--- a/src/watchFiles.ts
+++ b/src/watchFiles.ts
@@ -9,9 +9,9 @@ export function watchFiles(
   cb: () => void
 ) {
   const tsConfig = typescript.getTypescriptConfig(originalServicePath)
-  let watchFiles = typescript.getSourceFiles(rootFileNames, tsConfig)
+  let watchedFiles = typescript.getSourceFiles(rootFileNames, tsConfig)
 
-  watchFiles.forEach(fileName => {
+  watchedFiles.forEach(fileName => {
     watchFile(fileName, { persistent: true, interval: 250 }, watchCallback)
   })
 
@@ -25,18 +25,18 @@ export function watchFiles(
 
     // use can reference not watched yet file or remove reference to already watched
     const newWatchFiles =  typescript.getSourceFiles(rootFileNames, tsConfig)
-    watchFiles.forEach(fileName => {
+    watchedFiles.forEach(fileName => {
       if (newWatchFiles.indexOf(fileName) < 0) {
         unwatchFile(fileName, watchCallback)
       }
     })
 
     newWatchFiles.forEach(fileName => {
-      if (watchFiles.indexOf(fileName) < 0) {
+      if (watchedFiles.indexOf(fileName) < 0) {
         watchFile(fileName, { persistent: true, interval: 250 }, watchCallback)
       }
     })
 
-    watchFiles = newWatchFiles
+    watchedFiles = newWatchFiles
   }
 }
diff --git a/yarn.lock b/yarn.lock
index 46f0460..f534ae7 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -735,13 +735,6 @@ form-data@~2.1.1:
     combined-stream "^1.0.5"
     mime-types "^2.1.12"
 
-fs-extra@^2.0.0:
-  version "2.1.2"
-  resolved "https://registry.yarnpkg.com/fs-extra/-/fs-extra-2.1.2.tgz#046c70163cef9aad46b0e4a7fa467fb22d71de35"
-  dependencies:
-    graceful-fs "^4.1.2"
-    jsonfile "^2.1.0"
-
 fs-extra@^3.0.0:
   version "3.0.1"
   resolved "https://registry.yarnpkg.com/fs-extra/-/fs-extra-3.0.1.tgz#3794f378c58b342ea7dbbb23095109c4b3b62291"
@@ -750,11 +743,13 @@ fs-extra@^3.0.0:
     jsonfile "^3.0.0"
     universalify "^0.1.0"
 
-fs-p@2.0.0:
-  version "2.0.0"
-  resolved "https://registry.yarnpkg.com/fs-p/-/fs-p-2.0.0.tgz#66784a012473c700b68fb76ac2120eccc6b0602b"
+fs-extra@^4.0.2:
+  version "4.0.2"
+  resolved "https://registry.yarnpkg.com/fs-extra/-/fs-extra-4.0.2.tgz#f91704c53d1b461f893452b0c307d9997647ab6b"
   dependencies:
-    fs-extra "^2.0.0"
+    graceful-fs "^4.1.2"
+    jsonfile "^4.0.0"
+    universalify "^0.1.0"
 
 fs.realpath@^1.0.0:
   version "1.0.0"
@@ -1372,18 +1367,18 @@ json5@^0.5.0:
   version "0.5.1"
   resolved "https://registry.yarnpkg.com/json5/-/json5-0.5.1.tgz#1eade7acc012034ad84e2396767ead9fa5495821"
 
-jsonfile@^2.1.0:
-  version "2.4.0"
-  resolved "https://registry.yarnpkg.com/jsonfile/-/jsonfile-2.4.0.tgz#3736a2b428b87bbda0cc83b53fa3d633a35c2ae8"
-  optionalDependencies:
-    graceful-fs "^4.1.6"
-
 jsonfile@^3.0.0:
   version "3.0.0"
   resolved "https://registry.yarnpkg.com/jsonfile/-/jsonfile-3.0.0.tgz#92e7c7444e5ffd5fa32e6a9ae8b85034df8347d0"
   optionalDependencies:
     graceful-fs "^4.1.6"
 
+jsonfile@^4.0.0:
+  version "4.0.0"
+  resolved "https://registry.yarnpkg.com/jsonfile/-/jsonfile-4.0.0.tgz#8771aae0799b64076b76640fca058f9c10e33ecb"
+  optionalDependencies:
+    graceful-fs "^4.1.6"
+
 jsonify@~0.0.0:
   version "0.0.0"
   resolved "https://registry.yarnpkg.com/jsonify/-/jsonify-0.0.0.tgz#2c74b6ee41d93ca51b7b5aaee8f503631d252a73"