diff --git a/edit/source-editor.js b/edit/source-editor.js
index 36043916..3224acb8 100644
--- a/edit/source-editor.js
+++ b/edit/source-editor.js
@@ -23,12 +23,7 @@ function createSourceEditor(style) {
   });
 
   // normalize style
-  if (!style.id) {
-    setupNewStyle(style);
-  } else {
-    // style might be an object reference to background page
-    style = deepCopy(style);
-  }
+  if (!style.id) setupNewStyle(style);
 
   const cm = CodeMirror($('.single-editor'), {value: style.sourceCode});
   editors.push(cm);
@@ -195,7 +190,7 @@ function createSourceEditor(style) {
         history.replaceState({}, '', `?id=${newStyle.id}`);
       }
       sessionStorage.justEditedStyleId = newStyle.id;
-      style = deepCopy(newStyle);
+      style = newStyle;
       updateMeta();
     }
   }
@@ -222,7 +217,6 @@ function createSourceEditor(style) {
         sourceCode: code,
       }))
       .then(replaceStyle)
-      .then(() => cm.setOption('mode', cm.doc.mode))
       .catch(err => {
         if (err.message === t('styleMissingMeta', 'name')) {
           messageBox.confirm(t('usercssReplaceTemplateConfirmation')).then(ok => ok &&
diff --git a/install-usercss/install-usercss.js b/install-usercss/install-usercss.js
index c889b2d7..072db856 100644
--- a/install-usercss/install-usercss.js
+++ b/install-usercss/install-usercss.js
@@ -283,7 +283,7 @@
         ]))
       ).then(ok => ok &&
         API.saveUsercss(Object.assign(style, dup && {reason: 'update'}))
-          .then(r => install(r instanceof Object ? r : deepCopy(r)))
+          .then(install)
           .catch(err => messageBox.alert(t('styleInstallFailed', err)))
       );
     };
diff --git a/popup/popup.js b/popup/popup.js
index cecedc75..7e45de2f 100644
--- a/popup/popup.js
+++ b/popup/popup.js
@@ -366,7 +366,7 @@ Object.assign(handleEvent, {
     if (styleIsUsercss) {
       API.getStyles({id: styleId}).then(([style]) => {
         hotkeys.setState(false);
-        configDialog(deepCopy(style)).then(() => {
+        configDialog(style).then(() => {
           hotkeys.setState(true);
         });
       });