diff --git a/server/build/plugins/watch-pages-plugin.js b/server/build/plugins/watch-pages-plugin.js
index b1cc23e0e1..2e6a40990f 100644
--- a/server/build/plugins/watch-pages-plugin.js
+++ b/server/build/plugins/watch-pages-plugin.js
@@ -3,7 +3,7 @@ import { resolve, relative, join, extname } from 'path'
 export default class WatchPagesPlugin {
   constructor (dir) {
     this.dir = resolve(dir, 'pages')
-    this.prevFileDependencies = null
+    this.prevFileDependencies = []
   }
 
   apply (compiler) {