diff --git a/edit/source-editor.js b/edit/source-editor.js
index 1e53283a..6db47d40 100644
--- a/edit/source-editor.js
+++ b/edit/source-editor.js
@@ -123,7 +123,8 @@ function createSourceEditor(style) {
 
     chromeSync.getLZValue('usercssTemplate').then(code => {
       code = code || DEFAULT_CODE;
-      style.sourceCode = code.replace(/\s+$/, '\n\n') + section;
+      // strip the last dummy section if any, add an empty line followed by the section
+      style.sourceCode = code.replace(/@-moz-document[^{]*\{[^}]*\}\s*$|\s+$/g, '\n\n') + section;
       cm.startOperation();
       cm.setValue(style.sourceCode);
       cm.clearHistory();