diff --git a/lib/main.js b/lib/main.js
index 0ccdb16d..9754866e 100644
--- a/lib/main.js
+++ b/lib/main.js
@@ -343,7 +343,7 @@ so you can easily test run multiple events.
 
   _npmInstall (program, codeDirectory) {
     const dockerBaseOptions = [
-      'run', '--rm', '-v', `${codeDirectory}:/var/task`, '-w', '/var/task',
+      'run', '--rm', '-v', `${fs.realpathSync(codeDirectory)}:/var/task`, '-w', '/var/task',
       program.dockerImage,
       'npm', '-s', 'install', '--production'
     ]