diff --git a/src/advancedconfig.h b/src/advancedconfig.h
--- a/src/advancedconfig.h
+++ b/src/advancedconfig.h
@@ -37,7 +37,7 @@
     explicit AdvancedConfig(const KSharedConfigPtr &config, QWidget *parent = nullptr);
     ~AdvancedConfig();
 
-    QVariantMap save();
+    void save(QVariantMap &args);
 
 Q_SIGNALS:
     void changed(bool changed=true);
diff --git a/src/advancedconfig.cpp b/src/advancedconfig.cpp
--- a/src/advancedconfig.cpp
+++ b/src/advancedconfig.cpp
@@ -103,10 +103,8 @@
     configUi->rebootCommand->setUrl(QUrl::fromLocalFile(mConfig->group("General").readEntry("RebootCommand")));
 }
 
-QVariantMap AdvancedConfig::save()
+void AdvancedConfig::save(QVariantMap &args)
 {
-    QVariantMap args;
-
     args[QStringLiteral("kde_settings.conf/Autologin/User")] = ( configUi->autoLogin->isChecked() ) ? configUi->userList->currentText() : QString();
     args[QStringLiteral("kde_settings.conf/Autologin/Session")] = ( configUi->autoLogin->isChecked() ) ? configUi->sessionList->currentData() : QString();
 
@@ -122,8 +120,6 @@
 
     args[QStringLiteral("kde_settings.conf/General/HaltCommand")] = configUi->haltCommand->url().toLocalFile();
     args[QStringLiteral("kde_settings.conf/General/RebootCommand")] = configUi->rebootCommand->url().toLocalFile();
-
-    return args;
 }
 
 void AdvancedConfig::slotUidRangeChanged()
diff --git a/src/sddmkcm.cpp b/src/sddmkcm.cpp
--- a/src/sddmkcm.cpp
+++ b/src/sddmkcm.cpp
@@ -82,8 +82,8 @@
     }
 
     qDebug() << "Ovr:" << args[QStringLiteral("theme.conf.user")].toString();
-    args.unite(mThemeConfig->save());
-    args.unite(mAdvancedConfig->save());
+    mThemeConfig->save(args);
+    mAdvancedConfig->save(args);
 
     KAuth::Action saveAction = authAction();
 
diff --git a/src/themeconfig.h b/src/themeconfig.h
--- a/src/themeconfig.h
+++ b/src/themeconfig.h
@@ -34,7 +34,7 @@
     explicit ThemeConfig(const KSharedConfigPtr &config, QWidget *parent = nullptr);
     ~ThemeConfig();
 
-    QVariantMap save();
+    void save(QVariantMap &args);
     QString themeConfigPath() const;
 
 Q_SIGNALS:
diff --git a/src/themeconfig.cpp b/src/themeconfig.cpp
--- a/src/themeconfig.cpp
+++ b/src/themeconfig.cpp
@@ -70,15 +70,13 @@
     delete configUi;
 }
 
-QVariantMap ThemeConfig::save()
+void ThemeConfig::save(QVariantMap &args)
 {
     QModelIndex index = configUi->themesListView->currentIndex();
     if (!index.isValid()) {
-        return QVariantMap();
+        return;
     }
 
-    QVariantMap args;
-
     args[QStringLiteral("kde_settings.conf/Theme/Current")] = index.data(ThemesModel::IdRole);
 
     if (!mThemeConfigPath.isEmpty()) {
@@ -89,7 +87,6 @@
             args[QStringLiteral("theme.conf.user/General/type")] = QStringLiteral("color");
         }
     }
-    return args;
 }
 
 QString ThemeConfig::themeConfigPath() const