diff --git a/resources/externs/main.js b/resources/externs/main.js
new file mode 100644
index 000000000..be5aed904
--- /dev/null
+++ b/resources/externs/main.js
@@ -0,0 +1,29 @@
+var TopLevel = {
+  "offsetX": function() {},
+  "offsetY": function() {},
+  "nativeEvent": function() {},
+  "target": function() {},
+  "dataTransfer": function() {},
+  "dropEffect": function() {},
+  "value": function() {},
+  "offsetHeight": function() {},
+  "offsetWidth": function() {},
+  "scrollTop": function() {},
+  "scrollLeft": function() {},
+  "refs": function() {},
+  "ctrlKey": function() {},
+  "shiftKey": function() {},
+  "keyCode": function() {},
+  "currentTarget": function() {},
+  "createObjectURL": function() {},
+  "URL": function() {},
+  "innerHTML": function() {},
+  "getElementById": function() {},
+  "clientX": function() {},
+  "clientY": function() {},
+  "href": function() {},
+  "value": function() {},
+  "identifier": function() {},
+  "getBoundingClientRect": function() {},
+  "getBBox": function() {}
+};
diff --git a/scripts/dist.clj b/scripts/dist.clj
index 15a1c7ffa..b91f56cad 100644
--- a/scripts/dist.clj
+++ b/scripts/dist.clj
@@ -16,7 +16,9 @@
     :output-dir "resources/public/js"
     :closure-defines {"uxbox.repo.core.url"
                       "https://test.uxbox.io/api"}
-    :optimizations :simple
+    :optimizations :advanced
+    :externs ["externs/main.js"]
+    :source-map "resources/public/js/main.js.map"
     :static-fns true
     :language-in  :ecmascript5
     :language-out :ecmascript5