diff --git a/src/libs/utils/theme/theme.cpp b/src/libs/utils/theme/theme.cpp
index ccfba5f6fcc..b73510e9d62 100644
--- a/src/libs/utils/theme/theme.cpp
+++ b/src/libs/utils/theme/theme.cpp
@@ -65,10 +65,11 @@ void setCreatorTheme(Theme *theme)
     m_creatorTheme = theme;
 }
 
-Theme::Theme(QObject *parent)
+Theme::Theme(const QString &name, QObject *parent)
   : QObject(parent)
   , d(new ThemePrivate)
 {
+    d->name = name;
 }
 
 Theme::~Theme()
@@ -121,11 +122,16 @@ QPair<QColor, QString> Theme::readNamedColor(const QString &color) const
     return qMakePair(QColor::fromRgba(rgba), QString());
 }
 
-QString Theme::fileName() const
+QString Theme::filePath() const
 {
     return d->fileName;
 }
 
+QString Theme::name() const
+{
+    return d->name;
+}
+
 void Theme::setName(const QString &name)
 {
     d->name = name;
diff --git a/src/libs/utils/theme/theme.h b/src/libs/utils/theme/theme.h
index 8c6aa9bf630..d75962eb69e 100644
--- a/src/libs/utils/theme/theme.h
+++ b/src/libs/utils/theme/theme.h
@@ -54,7 +54,7 @@ class QTCREATOR_UTILS_EXPORT Theme : public QObject
     Q_ENUMS(WidgetStyle)
 
 public:
-    Theme(QObject *parent = 0);
+    Theme(const QString &name, QObject *parent = 0);
     ~Theme();
 
     enum Color {
@@ -203,7 +203,8 @@ public:
     QPalette palette() const;
     QStringList preferredStyles() const;
 
-    QString fileName() const;
+    QString filePath() const;
+    QString name() const;
     void setName(const QString &name);
 
     QVariantHash values() const;
@@ -215,15 +216,11 @@ public:
 
     ThemePrivate *d;
 
-signals:
-    void changed();
-
 private:
     QPair<QColor, QString> readNamedColor(const QString &color) const;
 };
 
 QTCREATOR_UTILS_EXPORT Theme *creatorTheme();
-QTCREATOR_UTILS_EXPORT void setCreatorTheme(Theme *theme);
 
 } // namespace Utils
 
diff --git a/src/libs/utils/theme/theme_p.h b/src/libs/utils/theme/theme_p.h
index bf78904e7ed..48a9a669bd1 100644
--- a/src/libs/utils/theme/theme_p.h
+++ b/src/libs/utils/theme/theme_p.h
@@ -55,6 +55,8 @@ public:
     QMap<QString, QColor> palette;
 };
 
+QTCREATOR_UTILS_EXPORT void setCreatorTheme(Theme *theme);
+
 } // namespace Utils
 
 #endif // THEME_P_H
diff --git a/src/plugins/coreplugin/coreplugin.cpp b/src/plugins/coreplugin/coreplugin.cpp
index e84be25ac64..3b6d055c991 100644
--- a/src/plugins/coreplugin/coreplugin.cpp
+++ b/src/plugins/coreplugin/coreplugin.cpp
@@ -48,6 +48,7 @@
 #include <utils/savefile.h>
 #include <utils/stringutils.h>
 #include <utils/theme/theme.h>
+#include <utils/theme/theme_p.h>
 
 #include <QtPlugin>
 #include <QDebug>
@@ -90,11 +91,36 @@ CorePlugin::~CorePlugin()
     setCreatorTheme(0);
 }
 
+static QString absoluteThemePath(const QString &themeName)
+{
+    if (themeName.isEmpty())
+        return themeName;
+    QString res = QDir::fromNativeSeparators(themeName);
+    QFileInfo fi(res);
+    // Try the given name
+    if (fi.exists())
+        return fi.absoluteFilePath();
+    const QString suffix = QLatin1String("creatortheme");
+    // Try name.creatortheme
+    if (fi.suffix() != suffix) {
+        res = themeName + QLatin1Char('.') + suffix;
+        fi.setFile(res);
+        if (fi.exists())
+            return fi.absoluteFilePath();
+    }
+    if (fi.path().isEmpty())
+        return QString(); // absolute/relative path, but not found
+    // If only name was given, look it up in qtcreator/themes
+    res.prepend(ICore::resourcePath() + QLatin1String("/themes/"));
+    return QFileInfo::exists(res) ? res : QString();
+}
+
 void CorePlugin::parseArguments(const QStringList &arguments)
 {
-    QString themeName = QLatin1String("default");
+    const QString defaultTheme = QLatin1String("default");
+    QString themeName = ICore::settings()->value(
+                QLatin1String(Constants::SETTINGS_THEME), defaultTheme).toString();
     QColor overrideColor;
-    bool overrideTheme = false;
     bool presentationMode = false;
 
     for (int i = 0; i < arguments.size(); ++i) {
@@ -106,34 +132,27 @@ void CorePlugin::parseArguments(const QStringList &arguments)
         if (arguments.at(i) == QLatin1String("-presentationMode"))
             presentationMode = true;
         if (arguments.at(i) == QLatin1String("-theme")) {
-            overrideTheme = true;
             themeName = arguments.at(i + 1);
             i++;
         }
     }
 
-    QSettings *settings = Core::ICore::settings();
-    QString themeURI = settings->value(QLatin1String(Core::Constants::SETTINGS_THEME)).toString();
-
-    if (!QFileInfo::exists(themeURI) || overrideTheme) {
-        const QString builtInTheme = QStringLiteral("%1/themes/%2.creatortheme")
-            .arg(ICore::resourcePath()).arg(themeName);
-        if (QFile::exists(builtInTheme)) {
-            themeURI = builtInTheme;
-        } else if (themeName.endsWith(QLatin1String(".creatortheme"))) {
-            themeURI = themeName;
-        } else { // TODO: Fallback to default theme
+    QString themeURI = absoluteThemePath(themeName);
+    if (themeURI.isEmpty()) {
+        themeName = defaultTheme;
+        themeURI = QStringLiteral("%1/themes/%2.creatortheme").arg(ICore::resourcePath()).arg(themeName);
+        if (themeURI.isEmpty()) {
             qCritical("%s", qPrintable(QCoreApplication::translate("Application", "No valid theme '%1'")
                                        .arg(themeName)));
         }
     }
 
     QSettings themeSettings(themeURI, QSettings::IniFormat);
-    Theme *theme = new Theme(qApp);
+    Theme *theme = new Theme(themeName, qApp);
     theme->readSettings(themeSettings);
-    setCreatorTheme(theme);
     if (theme->flag(Theme::ApplyThemePaletteGlobally))
-        QApplication::setPalette(creatorTheme()->palette());
+        QApplication::setPalette(theme->palette());
+    setCreatorTheme(theme);
 
     // defer creation of these widgets until here,
     // because they need a valid theme set
diff --git a/src/plugins/coreplugin/coreplugin.h b/src/plugins/coreplugin/coreplugin.h
index fafc896a0c7..ffc8df457e0 100644
--- a/src/plugins/coreplugin/coreplugin.h
+++ b/src/plugins/coreplugin/coreplugin.h
@@ -33,6 +33,8 @@
 
 #include <extensionsystem/iplugin.h>
 
+namespace Utils { class Theme; }
+
 namespace Core {
 
 class DesignMode;
diff --git a/src/plugins/coreplugin/icore.h b/src/plugins/coreplugin/icore.h
index 8014b1548e3..ce7fcd16587 100644
--- a/src/plugins/coreplugin/icore.h
+++ b/src/plugins/coreplugin/icore.h
@@ -139,6 +139,7 @@ signals:
     void coreAboutToClose();
     void contextAboutToChange(const QList<Core::IContext *> &context);
     void contextChanged(const QList<Core::IContext *> &context, const Core::Context &additionalContexts);
+    void themeChanged();
 };
 
 } // namespace Core
diff --git a/src/plugins/coreplugin/themeeditor/themesettingstablemodel.cpp b/src/plugins/coreplugin/themeeditor/themesettingstablemodel.cpp
index 87826f87bb4..ef921417594 100644
--- a/src/plugins/coreplugin/themeeditor/themesettingstablemodel.cpp
+++ b/src/plugins/coreplugin/themeeditor/themesettingstablemodel.cpp
@@ -267,7 +267,6 @@ void ThemeSettingsTableModel::toTheme(Theme *t) const
     theme->widgetStyle = m_widgetStyle;
     theme->name = m_name;
     theme->preferredStyles = m_preferredStyles;
-    emit t->changed();
 }
 
 Qt::ItemFlags ThemeSettingsTableModel::sectionHeaderFlags(int section) const
diff --git a/src/plugins/coreplugin/themesettingswidget.cpp b/src/plugins/coreplugin/themesettingswidget.cpp
index fd29e643639..200888762bd 100644
--- a/src/plugins/coreplugin/themesettingswidget.cpp
+++ b/src/plugins/coreplugin/themesettingswidget.cpp
@@ -31,9 +31,11 @@
 #include "themesettingswidget.h"
 #include "coreconstants.h"
 #include "icore.h"
+#include "manhattanstyle.h"
 #include "themeeditor/themesettingstablemodel.h"
 
 #include <utils/theme/theme.h>
+#include <utils/theme/theme_p.h>
 #include <utils/qtcassert.h>
 
 #include <QDebug>
@@ -41,6 +43,7 @@
 #include <QInputDialog>
 #include <QMessageBox>
 #include <QSettings>
+#include <QStyleFactory>
 
 #include "ui_themesettings.h"
 
@@ -53,9 +56,7 @@ const char themeNameKey[] = "ThemeName";
 
 static QString customThemesPath()
 {
-    QString path = Core::ICore::userResourcePath();
-    path.append(QLatin1String("/themes/"));
-    return path;
+    return ICore::userResourcePath() + QLatin1String("/themes/");
 }
 
 static QString createThemeFileName(const QString &pattern)
@@ -84,23 +85,27 @@ static QString createThemeFileName(const QString &pattern)
 struct ThemeEntry
 {
     ThemeEntry() {}
-    ThemeEntry(const QString &fileName, bool readOnly):
-        m_fileName(fileName),
+    ThemeEntry(const QString &name, const QString &filePath, bool readOnly):
+        m_name(name),
+        m_filePath(filePath),
         m_readOnly(readOnly)
-    { }
+    {
+    }
 
-    QString fileName() const { return m_fileName; }
-    QString name() const;
+    QString name() const { return m_name; }
+    QString displayName() const;
+    QString filePath() const { return m_filePath; }
     bool readOnly() const { return m_readOnly; }
 
 private:
-    QString m_fileName;
+    QString m_name;
+    QString m_filePath;
     bool m_readOnly;
 };
 
-QString ThemeEntry::name() const
+QString ThemeEntry::displayName() const
 {
-    QSettings settings(m_fileName, QSettings::IniFormat);
+    QSettings settings(filePath(), QSettings::IniFormat);
     QString n = settings.value(QLatin1String(themeNameKey), QCoreApplication::tr("unnamed")).toString();
     return m_readOnly ? QCoreApplication::tr("%1 (built-in)").arg(n) : n;
 }
@@ -122,7 +127,7 @@ public:
     QVariant data(const QModelIndex &index, int role) const
     {
         if (role == Qt::DisplayRole)
-            return m_themes.at(index.row()).name();
+            return m_themes.at(index.row()).displayName();
         return QVariant();
     }
 
@@ -168,7 +173,7 @@ ThemeSettingsPrivate::ThemeSettingsPrivate(QWidget *widget)
     , m_refreshingThemeList(false)
     , m_ui(new Ui::ThemeSettings)
 {
-    m_currentTheme = ThemeEntry(creatorTheme()->fileName(), true);
+    m_currentTheme = ThemeEntry(creatorTheme()->name(), creatorTheme()->filePath(), true);
     m_ui->setupUi(widget);
     m_ui->editor->hide(); // TODO: Restore after improving the editor
     m_ui->themeComboBox->setModel(m_themeListModel);
@@ -203,22 +208,24 @@ void ThemeSettingsWidget::refreshThemeList()
 {
     QList<ThemeEntry> themes;
 
-    QString resourcePath = Core::ICore::resourcePath();
-    QDir themeDir(resourcePath + QLatin1String("/themes"));
+    QDir themeDir(ICore::resourcePath() + QLatin1String("/themes"));
     themeDir.setNameFilters(QStringList() << QLatin1String("*.creatortheme"));
     themeDir.setFilter(QDir::Files);
 
     int selected = 0;
 
     QStringList themeList = themeDir.entryList();
-    QString defaultTheme = QFileInfo(defaultThemeFileName()).fileName();
-    if (themeList.removeAll(defaultTheme))
+    const QString defaultTheme = QLatin1String("default.creatortheme");
+    if (themeList.removeOne(defaultTheme))
         themeList.prepend(defaultTheme);
-    foreach (const QString &file, themeList) {
-        const QString fileName = themeDir.absoluteFilePath(file);
-        if (d->m_currentTheme.fileName() == fileName)
-            selected = themes.size();
-        themes.append(ThemeEntry(fileName, true));
+    const QLatin1String extension(".creatortheme");
+    for (int i = 0, total = themeList.count(); i < total; ++i) {
+        const QString fileName = themeList.at(i);
+        if (d->m_currentTheme.name() + extension == fileName)
+            selected = i;
+        QString name = fileName;
+        name.remove(extension);
+        themes.append(ThemeEntry(name, themeDir.absoluteFilePath(fileName), true));
     }
 
     if (themes.isEmpty())
@@ -227,9 +234,9 @@ void ThemeSettingsWidget::refreshThemeList()
     themeDir.setPath(customThemesPath());
     foreach (const QString &file, themeDir.entryList()) {
         const QString fileName = themeDir.absoluteFilePath(file);
-        if (d->m_currentTheme.fileName() == fileName)
+        if (d->m_currentTheme.name() == fileName)
             selected = themes.size();
-        themes.append(ThemeEntry(fileName, false));
+        themes.append(ThemeEntry(fileName, fileName, false));
     }
 
     d->m_currentTheme = themes[selected];
@@ -240,19 +247,6 @@ void ThemeSettingsWidget::refreshThemeList()
     d->m_refreshingThemeList = false;
 }
 
-QString ThemeSettingsWidget::defaultThemeFileName(const QString &fileName)
-{
-    QString defaultScheme = Core::ICore::resourcePath();
-    defaultScheme += QLatin1String("/themes/");
-
-    if (!fileName.isEmpty() && QFile::exists(defaultScheme + fileName))
-        defaultScheme += fileName;
-    else
-        defaultScheme += QLatin1String("default.creatortheme");
-
-    return defaultScheme;
-}
-
 void ThemeSettingsWidget::themeSelected(int index)
 {
     bool readOnly = true;
@@ -265,8 +259,8 @@ void ThemeSettingsWidget::themeSelected(int index)
         readOnly = entry.readOnly();
         d->m_currentTheme = entry;
 
-        QSettings settings(entry.fileName(), QSettings::IniFormat);
-        Theme theme;
+        QSettings settings(entry.filePath(), QSettings::IniFormat);
+        Theme theme(entry.name());
         theme.readSettings(settings);
         d->m_ui->editor->initFrom(&theme);
     }
@@ -288,7 +282,7 @@ void ThemeSettingsWidget::confirmDeleteTheme()
 
     QMessageBox *messageBox = new QMessageBox(QMessageBox::Warning,
                                               tr("Delete Theme"),
-                                              tr("Are you sure you want to delete the theme '%1' permanently?").arg(entry.name()),
+                                              tr("Are you sure you want to delete the theme '%1' permanently?").arg(entry.displayName()),
                                               QMessageBox::Discard | QMessageBox::Cancel,
                                               d->m_ui->deleteButton->window());
 
@@ -312,7 +306,7 @@ void ThemeSettingsWidget::deleteTheme()
     const ThemeEntry &entry = d->m_themeListModel->themeAt(index);
     QTC_ASSERT(!entry.readOnly(), return);
 
-    if (QFile::remove(entry.fileName()))
+    if (QFile::remove(entry.filePath()))
         d->m_themeListModel->removeTheme(index);
 }
 
@@ -339,7 +333,7 @@ void ThemeSettingsWidget::maybeSaveTheme()
     QMessageBox *messageBox = new QMessageBox(QMessageBox::Warning,
                                               tr("Theme Changed"),
                                               tr("The theme \"%1\" was modified, do you want to save the changes?")
-                                                  .arg(d->m_currentTheme.name()),
+                                                  .arg(d->m_currentTheme.displayName()),
                                               QMessageBox::Discard | QMessageBox::Save,
                                               d->m_ui->themeComboBox->window());
 
@@ -350,9 +344,9 @@ void ThemeSettingsWidget::maybeSaveTheme()
     messageBox->setDefaultButton(QMessageBox::Save);
 
     if (messageBox->exec() == QMessageBox::Save) {
-        Theme newTheme;
+        Theme newTheme(d->m_currentTheme.name());
         d->m_ui->editor->model()->toTheme(&newTheme);
-        newTheme.writeSettings(d->m_currentTheme.fileName());
+        newTheme.writeSettings(d->m_currentTheme.filePath());
     }
 }
 
@@ -378,10 +372,10 @@ void ThemeSettingsWidget::renameTheme()
         return;
 
     // overwrite file with new name
-    Theme newTheme;
+    Theme newTheme(entry.name());
     d->m_ui->editor->model()->toTheme(&newTheme);
     newTheme.setName(newName);
-    newTheme.writeSettings(entry.fileName());
+    newTheme.writeSettings(entry.filePath());
 
     refreshThemeList();
 }
@@ -394,7 +388,7 @@ void ThemeSettingsWidget::copyThemeByName(const QString &name)
 
     const ThemeEntry &entry = d->m_themeListModel->themeAt(index);
 
-    QString baseFileName = QFileInfo(entry.fileName()).completeBaseName();
+    QString baseFileName = QFileInfo(entry.filePath()).completeBaseName();
     baseFileName += QLatin1String("_copy%1.creatortheme");
     QString fileName = createThemeFileName(baseFileName);
 
@@ -404,36 +398,46 @@ void ThemeSettingsWidget::copyThemeByName(const QString &name)
     // Ask about saving any existing modifactions
     maybeSaveTheme();
 
-    Theme newTheme;
+    Theme newTheme(fileName);
     d->m_ui->editor->model()->toTheme(&newTheme);
     newTheme.setName(name);
     newTheme.writeSettings(fileName);
 
-    d->m_currentTheme = ThemeEntry(fileName, true);
+    d->m_currentTheme = ThemeEntry(fileName, fileName, true);
 
     refreshThemeList();
 }
 
 void ThemeSettingsWidget::apply()
 {
-    {
-        d->m_ui->editor->model()->toTheme(creatorTheme());
-        if (creatorTheme()->flag(Theme::ApplyThemePaletteGlobally))
-            QApplication::setPalette(creatorTheme()->palette());
-        foreach (QWidget *w, QApplication::topLevelWidgets())
-            w->update();
+    const QString themeName = d->m_currentTheme.name();
+    Theme *newTheme = new Theme(themeName);
+    if (d->m_currentTheme.readOnly()) {
+        QSettings themeSettings(d->m_currentTheme.filePath(), QSettings::IniFormat);
+        newTheme->readSettings(themeSettings);
+    } else {
+        d->m_ui->editor->model()->toTheme(newTheme);
+        newTheme->writeSettings(d->m_currentTheme.filePath());
     }
-
-    // save definition of theme
-    if (!d->m_currentTheme.readOnly()) {
-        Theme newTheme;
-        d->m_ui->editor->model()->toTheme(&newTheme);
-        newTheme.writeSettings(d->m_currentTheme.fileName());
+    setCreatorTheme(newTheme);
+    emit ICore::instance()->themeChanged();
+    QPalette pal = newTheme->flag(Theme::ApplyThemePaletteGlobally) ? newTheme->palette()
+                                                                    : Theme::initialPalette();
+    QApplication::setPalette(pal);
+    if (ManhattanStyle *style = qobject_cast<ManhattanStyle *>(QApplication::style())) {
+        QStyle *baseStyle = 0;
+        foreach (const QString &s, creatorTheme()->preferredStyles()) {
+            if ((baseStyle = QStyleFactory::create(s)))
+                break;
+        }
+        style->setBaseStyle(baseStyle);
     }
+    foreach (QWidget *w, QApplication::topLevelWidgets())
+        w->update();
 
     // save filename of selected theme in global config
     QSettings *settings = Core::ICore::settings();
-    settings->setValue(QLatin1String(Core::Constants::SETTINGS_THEME), d->m_currentTheme.fileName());
+    settings->setValue(QLatin1String(Core::Constants::SETTINGS_THEME), themeName);
 }
 
 } // namespace Internal
diff --git a/src/plugins/coreplugin/themesettingswidget.h b/src/plugins/coreplugin/themesettingswidget.h
index 8ed5dd882d1..24ce6a2f01d 100644
--- a/src/plugins/coreplugin/themesettingswidget.h
+++ b/src/plugins/coreplugin/themesettingswidget.h
@@ -46,8 +46,6 @@ public:
     ThemeSettingsWidget(QWidget *parent = 0);
     ~ThemeSettingsWidget();
 
-    static QString defaultThemeFileName(const QString &fileName = QString());
-
     void apply();
 
 private slots:
diff --git a/src/plugins/welcome/welcomeplugin.cpp b/src/plugins/welcome/welcomeplugin.cpp
index c4d64f6d439..0364836925f 100644
--- a/src/plugins/welcome/welcomeplugin.cpp
+++ b/src/plugins/welcome/welcomeplugin.cpp
@@ -258,7 +258,7 @@ void WelcomeMode::initPlugins()
     ctx->setContextProperty(QLatin1String("pagesModel"), QVariant::fromValue(m_pluginList));
 
     onThemeChanged();
-    connect(creatorTheme(), &Theme::changed, this, &WelcomeMode::onThemeChanged);
+    connect(Core::ICore::instance(), &Core::ICore::themeChanged, this, &WelcomeMode::onThemeChanged);
     ctx->setContextProperty(QLatin1String("creatorTheme"), &m_themeProperties);
 
     QString path = resourcePath() + QLatin1String("/welcomescreen/welcomescreen.qml");