diff --git a/lib/main.js b/lib/main.js
index 0c1b7415..7d943a4d 100644
--- a/lib/main.js
+++ b/lib/main.js
@@ -317,7 +317,7 @@ so you can easily test run multiple events.
 
   _npmInstall (program, codeDirectory) {
     const dockerBaseOptions = [
-      'run', '--rm', '-v', `${codeDirectory}:/var/task`,
+      'run', '--rm', '-v', `${codeDirectory}:/var/task`, '-w', '/var/task',
       program.dockerImage,
       'npm', '-s', 'install', '--production'
     ]