diff --git a/ksplash/ksplashqml/splashapp.h b/ksplash/ksplashqml/splashapp.h
--- a/ksplash/ksplashqml/splashapp.h
+++ b/ksplash/ksplashqml/splashapp.h
@@ -64,6 +64,7 @@
     bool m_window;
     QStringList m_stages;
     QBasicTimer m_timer;
+    QString m_theme;
 
     KWayland::Client::PlasmaShell *m_waylandPlasmaShell = nullptr;
 
diff --git a/ksplash/ksplashqml/splashapp.cpp b/ksplash/ksplashqml/splashapp.cpp
--- a/ksplash/ksplashqml/splashapp.cpp
+++ b/ksplash/ksplashqml/splashapp.cpp
@@ -57,11 +57,13 @@
     parser.addOption(QCommandLineOption(QStringLiteral("window"), QStringLiteral("Run in windowed mode")));
     parser.addOption(QCommandLineOption(QStringLiteral("nofork"), QStringLiteral("Don't fork")));
     parser.addOption(QCommandLineOption(QStringLiteral("pid"), QStringLiteral("Print the pid of the child process")));
+    parser.addPositionalArgument(QStringLiteral("theme"), QStringLiteral("Path to the theme to test"));
     parser.addHelpOption();
 
     parser.process(*this);
     m_testing = parser.isSet(QStringLiteral("test"));
     m_window = parser.isSet(QStringLiteral("window"));
+    m_theme = parser.positionalArguments().value(0);
 
     setupWaylandIntegration();
 
@@ -134,7 +136,7 @@
 
 void SplashApp::adoptScreen(QScreen* screen)
 {
-    SplashWindow *w = new SplashWindow(m_testing, m_window);
+    SplashWindow *w = new SplashWindow(m_testing, m_window, m_theme);
     w->setGeometry(screen->geometry());
     w->setStage(m_stage);
     w->setVisible(true);
diff --git a/ksplash/ksplashqml/splashwindow.h b/ksplash/ksplashqml/splashwindow.h
--- a/ksplash/ksplashqml/splashwindow.h
+++ b/ksplash/ksplashqml/splashwindow.h
@@ -37,7 +37,7 @@
 class SplashWindow: public KQuickAddons::QuickViewSharedEngine
 {
 public:
-    SplashWindow(bool testing = false, bool window = false);
+    SplashWindow(bool testing, bool window, const QString &theme);
 
     void setStage(int stage);
     virtual void setGeometry(const QRect &rect);
@@ -50,8 +50,9 @@
 private:
     void setupWaylandIntegration();
     int m_stage;
-    bool m_testing;
-    bool m_window;
+    const bool m_testing;
+    const bool m_window;
+    const QString m_theme;
     KWayland::Client::PlasmaShellSurface *m_shellSurface = nullptr;
 };
 
diff --git a/ksplash/ksplashqml/splashwindow.cpp b/ksplash/ksplashqml/splashwindow.cpp
--- a/ksplash/ksplashqml/splashwindow.cpp
+++ b/ksplash/ksplashqml/splashwindow.cpp
@@ -20,7 +20,6 @@
 #include "splashwindow.h"
 #include "splashapp.h"
 
-#include <QGuiApplication>
 #include <QQmlContext>
 #include <QQuickItem>
 #include <QKeyEvent>
@@ -38,11 +37,12 @@
 #include <KWayland/Client/plasmashell.h>
 #include <KWindowSystem>
 
-SplashWindow::SplashWindow(bool testing, bool window)
+SplashWindow::SplashWindow(bool testing, bool window, const QString &theme)
     : KQuickAddons::QuickViewSharedEngine(),
       m_stage(0),
       m_testing(testing),
-      m_window(window)
+      m_window(window),
+      m_theme(theme)
 {
     setColor(Qt::transparent);
     setDefaultAlphaBuffer(true);
@@ -126,13 +126,13 @@
         const QString packageName = cg.readEntry("LookAndFeelPackage", QString());
         if (!packageName.isEmpty()) {
             package.setPath(packageName);
-        };
+        }
 
-        const QString theme = QGuiApplication::arguments().at(1);
-        if (!theme.startsWith(QLatin1String("--"))) {
-            package.setPath(theme);
+        if (!m_theme.isEmpty()) {
+            package.setPath(m_theme);
         }
 
+        Q_ASSERT(package.isValid());
         setSource(QUrl::fromLocalFile(package.filePath("splashmainscript")));
     }