diff --git a/edit/source-editor.js b/edit/source-editor.js
index 1c31a0c5..4f6ee180 100644
--- a/edit/source-editor.js
+++ b/edit/source-editor.js
@@ -215,6 +215,7 @@ function createSourceEditor(style) {
         sourceCode: cm.getValue(),
       }))
       .then(replaceStyle)
+      .then(() => cm.setOption('mode', cm.doc.mode))
       .catch(err => {
         if (err.message === t('styleMissingMeta', 'name')) {
           messageBox.confirm(t('usercssReplaceTemplateConfirmation')).then(ok => ok &&