diff --git a/development_server.js b/development_server.js
index d14bd6af1..0ba021c9e 100644
--- a/development_server.js
+++ b/development_server.js
@@ -63,7 +63,8 @@ function build() {
         bundle.write({
             format: 'iife',
             dest: 'dist/iD.js',
-            sourceMap: true
+            sourceMap: true,
+            useStrict: false
         });
         building = false;