diff --git a/plugins/lunchmealplugin/lunchmealsettings.cpp b/plugins/lunchmealplugin/lunchmealsettings.cpp
index 9c3dcc1..3703770 100644
--- a/plugins/lunchmealplugin/lunchmealsettings.cpp
+++ b/plugins/lunchmealplugin/lunchmealsettings.cpp
@@ -19,13 +19,28 @@ QString LunchMealSettings::url() const
     return m_settings.value(m_url, m_defaultUrl).toString();
 }
 
-void LunchMealSettings::setUrl(const QString &url)
+bool LunchMealSettings::setUrl(const QString &url)
 {
-    if(this->url() != url)
-    {
-        m_settings.setValue(QStringLiteral("LunchMealPlugin/url"), url);
+    if(this->url() == url)
+        return true;
+
+    if(url == m_defaultUrl)
+        m_settings.remove(m_url);
+    else
+        m_settings.setValue(m_url, url);
+
+    m_settings.sync();
+
+    const auto success = m_settings.status() == QSettings::NoError;
+    if(success)
         Q_EMIT urlChanged(url);
+    else
+    {
+        Q_EMIT m_settings.saveErrorOccured();
+        Q_EMIT saveErrorOccured();
     }
+
+    return success;
 }
 
 QString LunchMealSettings::dateFormat() const
@@ -33,11 +48,26 @@ QString LunchMealSettings::dateFormat() const
     return m_settings.value(m_dateFormat, m_defaultDateFormat).toString();
 }
 
-void LunchMealSettings::setDateFormat(const QString &dateFormat)
+bool LunchMealSettings::setDateFormat(const QString &dateFormat)
 {
-    if(this->dateFormat() != dateFormat)
-    {
-        m_settings.setValue(QStringLiteral("LunchMealPlugin/dateFormat"), dateFormat);
+    if(this->dateFormat() == dateFormat)
+        return true;
+
+    if(dateFormat == m_defaultDateFormat)
+        m_settings.remove(m_dateFormat);
+    else
+        m_settings.setValue(m_dateFormat, dateFormat);
+
+    m_settings.sync();
+
+    const auto success = m_settings.status() == QSettings::NoError;
+    if(success)
         Q_EMIT dateFormatChanged(dateFormat);
+    else
+    {
+        Q_EMIT m_settings.saveErrorOccured();
+        Q_EMIT saveErrorOccured();
     }
+
+    return success;
 }
diff --git a/plugins/lunchmealplugin/lunchmealsettings.h b/plugins/lunchmealplugin/lunchmealsettings.h
index 7db1913..6c8eec5 100644
--- a/plugins/lunchmealplugin/lunchmealsettings.h
+++ b/plugins/lunchmealplugin/lunchmealsettings.h
@@ -16,12 +16,14 @@ public:
 
     // no QString becuase placeholder %0 encodes wrong in urls!
     QString url() const;
-    void setUrl(const QString &url);
+    bool setUrl(const QString &url);
 
     QString dateFormat() const;
-    void setDateFormat(const QString &dateFormat);
+    bool setDateFormat(const QString &dateFormat);
 
 Q_SIGNALS:
+    void saveErrorOccured();
+
     void urlChanged(const QString &url);
     void dateFormatChanged(const QString &dateFormat);
 
diff --git a/plugins/lunchmealplugin/lunchmealsettingswidget.cpp b/plugins/lunchmealplugin/lunchmealsettingswidget.cpp
index a1edbb2..6f5754b 100644
--- a/plugins/lunchmealplugin/lunchmealsettingswidget.cpp
+++ b/plugins/lunchmealplugin/lunchmealsettingswidget.cpp
@@ -29,8 +29,8 @@ bool LunchMealSettingsWidget::isValid(QString &message) const
     return valid;
 }
 
-void LunchMealSettingsWidget::apply()
+bool LunchMealSettingsWidget::apply()
 {
-    m_settings.setUrl(m_lineEditUrl->text());
-    m_settings.setDateFormat(m_lineEditDateFormat->text());
+    return m_settings.setUrl(m_lineEditUrl->text()) &&
+           m_settings.setDateFormat(m_lineEditDateFormat->text());
 }
diff --git a/plugins/lunchmealplugin/lunchmealsettingswidget.h b/plugins/lunchmealplugin/lunchmealsettingswidget.h
index 72d99d6..779125d 100644
--- a/plugins/lunchmealplugin/lunchmealsettingswidget.h
+++ b/plugins/lunchmealplugin/lunchmealsettingswidget.h
@@ -16,7 +16,7 @@ public:
     virtual bool isValid(QString &message) const Q_DECL_OVERRIDE;
 
 public Q_SLOTS:
-    virtual void apply() Q_DECL_OVERRIDE;
+    virtual bool apply() Q_DECL_OVERRIDE;
 
 private:
     LunchMealSettings m_settings;
diff --git a/plugins/presenceplugin/presencesettings.cpp b/plugins/presenceplugin/presencesettings.cpp
index d1e315c..ba61eaf 100644
--- a/plugins/presenceplugin/presencesettings.cpp
+++ b/plugins/presenceplugin/presencesettings.cpp
@@ -17,11 +17,26 @@ int PresenceSettings::interval() const
     return m_settings.value(m_interval, m_defaultInterval).toInt();
 }
 
-void PresenceSettings::setInterval(int interval)
+bool PresenceSettings::setInterval(int interval)
 {
-    if(this->interval() != interval)
-    {
+    if(this->interval() == interval)
+        return true;
+
+    if(interval == m_defaultInterval)
+        m_settings.remove(m_interval);
+    else
         m_settings.setValue(m_interval, interval);
+
+    m_settings.sync();
+
+    const auto success = m_settings.status() == QSettings::NoError;
+    if(success)
         Q_EMIT intervalChanged(interval);
+    else
+    {
+        Q_EMIT m_settings.saveErrorOccured();
+        Q_EMIT saveErrorOccured();
     }
+
+    return success;
 }
diff --git a/plugins/presenceplugin/presencesettings.h b/plugins/presenceplugin/presencesettings.h
index 1fb2610..58f83ad 100644
--- a/plugins/presenceplugin/presencesettings.h
+++ b/plugins/presenceplugin/presencesettings.h
@@ -13,9 +13,11 @@ public:
     PresenceSettings(ZeiterfassungSettings &settings, QObject *parent = Q_NULLPTR);
 
     int interval() const;
-    void setInterval(int interval);
+    bool setInterval(int interval);
 
 Q_SIGNALS:
+    void saveErrorOccured();
+
     void intervalChanged(int interval);
 
 private:
diff --git a/plugins/presenceplugin/presencesettingswidget.cpp b/plugins/presenceplugin/presencesettingswidget.cpp
index b86c817..51b2733 100644
--- a/plugins/presenceplugin/presencesettingswidget.cpp
+++ b/plugins/presenceplugin/presencesettingswidget.cpp
@@ -18,13 +18,7 @@ PresenceSettingsWidget::PresenceSettingsWidget(ZeiterfassungSettings &settings,
     setLayout(layout);
 }
 
-bool PresenceSettingsWidget::isValid(QString &message) const
+bool PresenceSettingsWidget::apply()
 {
-    Q_UNUSED(message)
-    return true;
-}
-
-void PresenceSettingsWidget::apply()
-{
-    m_settings.setInterval(m_spinBox->value());
+    return m_settings.setInterval(m_spinBox->value());
 }
diff --git a/plugins/presenceplugin/presencesettingswidget.h b/plugins/presenceplugin/presencesettingswidget.h
index 5427b32..c9d649b 100644
--- a/plugins/presenceplugin/presencesettingswidget.h
+++ b/plugins/presenceplugin/presencesettingswidget.h
@@ -13,10 +13,8 @@ class PresenceSettingsWidget : public SettingsWidget
 public:
     explicit PresenceSettingsWidget(ZeiterfassungSettings &settings, QWidget *parent = Q_NULLPTR);
 
-    virtual bool isValid(QString &message) const Q_DECL_OVERRIDE;
-
 public Q_SLOTS:
-    virtual void apply() Q_DECL_OVERRIDE;
+    virtual bool apply() Q_DECL_OVERRIDE;
 
 private:
     PresenceSettings m_settings;
diff --git a/plugins/updaterplugin/updatersettings.cpp b/plugins/updaterplugin/updatersettings.cpp
index 2ea0fff..9d439e0 100644
--- a/plugins/updaterplugin/updatersettings.cpp
+++ b/plugins/updaterplugin/updatersettings.cpp
@@ -18,13 +18,28 @@ QUrl UpdaterSettings::url() const
     return m_settings.value(m_url, m_defaultUrl).toUrl();
 }
 
-void UpdaterSettings::setUrl(const QUrl &url)
+bool UpdaterSettings::setUrl(const QUrl &url)
 {
-    if(this->url() != url)
-    {
+    if(this->url() == url)
+        return true;
+
+    if(url == m_defaultUrl)
+        m_settings.remove(m_url);
+    else
         m_settings.setValue(m_url, url);
+
+    m_settings.sync();
+
+    const auto success = m_settings.status() == QSettings::NoError;
+    if(success)
         Q_EMIT urlChanged(url);
+    else
+    {
+        Q_EMIT m_settings.saveErrorOccured();
+        Q_EMIT saveErrorOccured();
     }
+
+    return success;
 }
 
 QDate UpdaterSettings::lastUpdateCheck() const
@@ -32,11 +47,26 @@ QDate UpdaterSettings::lastUpdateCheck() const
     return m_settings.value(m_lastUpdateCheck).toDate();
 }
 
-void UpdaterSettings::setLastUpdateCheck(const QDate &lastUpdateCheck)
+bool UpdaterSettings::setLastUpdateCheck(const QDate &lastUpdateCheck)
 {
-    if(this->lastUpdateCheck() != lastUpdateCheck)
-    {
+    if(this->lastUpdateCheck() == lastUpdateCheck)
+        return true;
+
+    if(!lastUpdateCheck.isValid())
+        m_settings.remove(m_lastUpdateCheck);
+    else
         m_settings.setValue(m_lastUpdateCheck, lastUpdateCheck);
+
+    m_settings.sync();
+
+    const auto success = m_settings.status() == QSettings::NoError;
+    if(success)
         Q_EMIT lastUpdateCheckChanged(lastUpdateCheck);
+    else
+    {
+        Q_EMIT m_settings.saveErrorOccured();
+        Q_EMIT saveErrorOccured();
     }
+
+    return success;
 }
diff --git a/plugins/updaterplugin/updatersettings.h b/plugins/updaterplugin/updatersettings.h
index 0eca1e4..f6998eb 100644
--- a/plugins/updaterplugin/updatersettings.h
+++ b/plugins/updaterplugin/updatersettings.h
@@ -16,12 +16,14 @@ public:
     explicit UpdaterSettings(ZeiterfassungSettings &settings, QObject *parent = Q_NULLPTR);
 
     QUrl url() const;
-    void setUrl(const QUrl &url);
+    bool setUrl(const QUrl &url);
 
     QDate lastUpdateCheck() const;
-    void setLastUpdateCheck(const QDate &lastUpdateCheck);
+    bool setLastUpdateCheck(const QDate &lastUpdateCheck);
 
 Q_SIGNALS:
+    void saveErrorOccured();
+
     void urlChanged(const QUrl &url);
     void lastUpdateCheckChanged(const QDate &lastUpdateCheck);
 
diff --git a/plugins/updaterplugin/updatersettingswidget.cpp b/plugins/updaterplugin/updatersettingswidget.cpp
index 1b0c63b..883bcc1 100644
--- a/plugins/updaterplugin/updatersettingswidget.cpp
+++ b/plugins/updaterplugin/updatersettingswidget.cpp
@@ -26,7 +26,7 @@ bool UpdaterSettingsWidget::isValid(QString &message) const
     return valid;
 }
 
-void UpdaterSettingsWidget::apply()
+bool UpdaterSettingsWidget::apply()
 {
-    m_settings.setUrl(QUrl(m_lineEdit->text()));
+    return m_settings.setUrl(QUrl(m_lineEdit->text()));
 }
diff --git a/plugins/updaterplugin/updatersettingswidget.h b/plugins/updaterplugin/updatersettingswidget.h
index 74a938e..a3568d2 100644
--- a/plugins/updaterplugin/updatersettingswidget.h
+++ b/plugins/updaterplugin/updatersettingswidget.h
@@ -16,7 +16,7 @@ public:
     virtual bool isValid(QString &message) const Q_DECL_OVERRIDE;
 
 public Q_SLOTS:
-    virtual void apply() Q_DECL_OVERRIDE;
+    virtual bool apply() Q_DECL_OVERRIDE;
 
 private:
     UpdaterSettings m_settings;
diff --git a/plugins/weatherplugin/weathersettings.cpp b/plugins/weatherplugin/weathersettings.cpp
index fc9a99c..71332df 100644
--- a/plugins/weatherplugin/weathersettings.cpp
+++ b/plugins/weatherplugin/weathersettings.cpp
@@ -17,11 +17,26 @@ QUrl WeatherSettings::url() const
     return m_settings.value(m_url, m_defaultUrl).toUrl();
 }
 
-void WeatherSettings::setUrl(const QUrl &url)
+bool WeatherSettings::setUrl(const QUrl &url)
 {
-    if(this->url() != url)
-    {
+    if(this->url() == url)
+        return true;
+
+    if(url == m_defaultUrl)
+        m_settings.remove(m_url);
+    else
         m_settings.setValue(m_url, url);
+
+    m_settings.sync();
+
+    const auto success = m_settings.status() == QSettings::NoError;
+    if(success)
         Q_EMIT urlChanged(url);
+    else
+    {
+        Q_EMIT m_settings.saveErrorOccured();
+        Q_EMIT saveErrorOccured();
     }
+
+    return success;
 }
diff --git a/plugins/weatherplugin/weathersettings.h b/plugins/weatherplugin/weathersettings.h
index c137b6f..aa9fb2f 100644
--- a/plugins/weatherplugin/weathersettings.h
+++ b/plugins/weatherplugin/weathersettings.h
@@ -14,9 +14,11 @@ public:
     WeatherSettings(ZeiterfassungSettings &settings, QObject *parent = Q_NULLPTR);
 
     QUrl url() const;
-    void setUrl(const QUrl &url);
+    bool setUrl(const QUrl &url);
 
 Q_SIGNALS:
+    void saveErrorOccured();
+
     void urlChanged(const QUrl &url);
 
 private:
diff --git a/plugins/weatherplugin/weathersettingswidget.cpp b/plugins/weatherplugin/weathersettingswidget.cpp
index 2e14db6..35f3cb5 100644
--- a/plugins/weatherplugin/weathersettingswidget.cpp
+++ b/plugins/weatherplugin/weathersettingswidget.cpp
@@ -26,7 +26,7 @@ bool WeatherSettingsWidget::isValid(QString &message) const
     return valid;
 }
 
-void WeatherSettingsWidget::apply()
+bool WeatherSettingsWidget::apply()
 {
-    m_settings.setUrl(QUrl::fromUserInput(m_lineEdit->text()));
+    return m_settings.setUrl(QUrl::fromUserInput(m_lineEdit->text()));
 }
diff --git a/plugins/weatherplugin/weathersettingswidget.h b/plugins/weatherplugin/weathersettingswidget.h
index b1688a6..7936f48 100644
--- a/plugins/weatherplugin/weathersettingswidget.h
+++ b/plugins/weatherplugin/weathersettingswidget.h
@@ -20,7 +20,7 @@ public:
     bool isValid(QString &message) const Q_DECL_OVERRIDE;
 
 public Q_SLOTS:
-    void apply() Q_DECL_OVERRIDE;
+    virtual bool apply() Q_DECL_OVERRIDE;
 
 private:
     WeatherSettings m_settings;
diff --git a/plugins/webradioplugin/webradiosettings.cpp b/plugins/webradioplugin/webradiosettings.cpp
index 8b65a3a..615c44a 100644
--- a/plugins/webradioplugin/webradiosettings.cpp
+++ b/plugins/webradioplugin/webradiosettings.cpp
@@ -31,13 +31,28 @@ QStringList WebRadioSettings::urls() const
     return m_settings.value(m_urls, m_defaultUrls).toStringList();
 }
 
-void WebRadioSettings::setUrls(const QStringList &urls)
+bool WebRadioSettings::setUrls(const QStringList &urls)
 {
-    if(this->urls() != urls)
-    {
+    if(this->urls() == urls)
+        return true;
+
+    if(urls == m_defaultUrls)
+        m_settings.remove(m_urls);
+    else
         m_settings.setValue(m_urls, urls);
+
+    m_settings.sync();
+
+    const auto success = m_settings.status() == QSettings::NoError;
+    if(success)
         Q_EMIT urlsChanged(urls);
+    else
+    {
+        Q_EMIT m_settings.saveErrorOccured();
+        Q_EMIT saveErrorOccured();
     }
+
+    return success;
 }
 
 QString WebRadioSettings::lastUrl() const
@@ -45,13 +60,28 @@ QString WebRadioSettings::lastUrl() const
     return m_settings.value(m_lastUrl).toString();
 }
 
-void WebRadioSettings::setLastUrl(const QString &lastUrl)
+bool WebRadioSettings::setLastUrl(const QString &lastUrl)
 {
-    if(this->lastUrl() != lastUrl)
-    {
+    if(this->lastUrl() == lastUrl)
+        return true;
+
+    if(lastUrl.isNull())
+        m_settings.remove(m_lastUrl);
+    else
         m_settings.setValue(m_lastUrl, lastUrl);
+
+    m_settings.sync();
+
+    const auto success = m_settings.status() == QSettings::NoError;
+    if(success)
         Q_EMIT lastUrlChanged(lastUrl);
+    else
+    {
+        Q_EMIT m_settings.saveErrorOccured();
+        Q_EMIT saveErrorOccured();
     }
+
+    return success;
 }
 
 int WebRadioSettings::volume() const
@@ -59,11 +89,26 @@ int WebRadioSettings::volume() const
     return m_settings.value(m_volume, m_defaultVolume).toInt();
 }
 
-void WebRadioSettings::setVolume(int volume)
+bool WebRadioSettings::setVolume(int volume)
 {
-    if(this->volume() != volume)
-    {
+    if(this->volume() == volume)
+        return true;
+
+    if(volume == m_defaultVolume)
+        m_settings.remove(m_volume);
+    else
         m_settings.setValue(m_volume, volume);
+
+    m_settings.sync();
+
+    const auto success = m_settings.status() == QSettings::NoError;
+    if(success)
         Q_EMIT volumeChanged(volume);
+    else
+    {
+        Q_EMIT m_settings.saveErrorOccured();
+        Q_EMIT saveErrorOccured();
     }
+
+    return success;
 }
diff --git a/plugins/webradioplugin/webradiosettings.h b/plugins/webradioplugin/webradiosettings.h
index 12c9ad7..0e8ceb6 100644
--- a/plugins/webradioplugin/webradiosettings.h
+++ b/plugins/webradioplugin/webradiosettings.h
@@ -16,15 +16,17 @@ public:
     WebRadioSettings(ZeiterfassungSettings &settings, QObject *parent = Q_NULLPTR);
 
     QStringList urls() const;
-    void setUrls(const QStringList &urls);
+    bool setUrls(const QStringList &urls);
 
     QString lastUrl() const;
-    void setLastUrl(const QString &lastUrl);
+    bool setLastUrl(const QString &lastUrl);
 
     int volume() const;
-    void setVolume(int volume);
+    bool setVolume(int volume);
 
 Q_SIGNALS:
+    void saveErrorOccured();
+
     void urlsChanged(const QStringList &urls);
     void lastUrlChanged(const QString &lastUrl);
     void volumeChanged(int volume);
diff --git a/plugins/webradioplugin/webradiosettingswidget.cpp b/plugins/webradioplugin/webradiosettingswidget.cpp
index c66eff1..adec37d 100644
--- a/plugins/webradioplugin/webradiosettingswidget.cpp
+++ b/plugins/webradioplugin/webradiosettingswidget.cpp
@@ -31,8 +31,7 @@ bool WebRadioSettingsWidget::isValid(QString &message) const
     return true;
 }
 
-void WebRadioSettingsWidget::apply()
+bool WebRadioSettingsWidget::apply()
 {
-    if(m_urlsWidget->stringList() != m_settings.urls())
-        m_settings.setUrls(m_urlsWidget->stringList());
+    return m_settings.setUrls(m_urlsWidget->stringList());
 }
diff --git a/plugins/webradioplugin/webradiosettingswidget.h b/plugins/webradioplugin/webradiosettingswidget.h
index d1f77dc..d3556ee 100644
--- a/plugins/webradioplugin/webradiosettingswidget.h
+++ b/plugins/webradioplugin/webradiosettingswidget.h
@@ -20,7 +20,7 @@ public:
     bool isValid(QString &message) const Q_DECL_OVERRIDE;
 
 public Q_SLOTS:
-    void apply() Q_DECL_OVERRIDE;
+    virtual bool apply() Q_DECL_OVERRIDE;
 
 private:
     WebRadioSettings m_settings;
diff --git a/zeiterfassungcorelib/zeiterfassungsettings.cpp b/zeiterfassungcorelib/zeiterfassungsettings.cpp
index 8f6aa6c..590872f 100644
--- a/zeiterfassungcorelib/zeiterfassungsettings.cpp
+++ b/zeiterfassungcorelib/zeiterfassungsettings.cpp
@@ -1,5 +1,7 @@
 #include "zeiterfassungsettings.h"
 
+#include <QDebug>
+
 const QString ZeiterfassungSettings::m_language("language");
 const QString ZeiterfassungSettings::m_url("url");
 const QString ZeiterfassungSettings::m_username("username");
@@ -48,16 +50,25 @@ QLocale::Language ZeiterfassungSettings::language() const
     return value(m_language, m_defaultLanguage).value<QLocale::Language>();
 }
 
-void ZeiterfassungSettings::setLanguage(QLocale::Language language)
+bool ZeiterfassungSettings::setLanguage(QLocale::Language language)
 {
-    if(this->language() != language)
-    {
-        if(m_defaultLanguage == language)
-            remove(m_language);
-        else
-            setValue(m_language, language);
+    if(this->language() == language)
+        return true;
+
+    if(m_defaultLanguage == language)
+        remove(m_language);
+    else
+        setValue(m_language, language);
+
+    sync();
+
+    const auto success = status() == QSettings::NoError;
+    if(success)
         Q_EMIT languageChanged(language);
-    }
+    else
+        Q_EMIT saveErrorOccured();
+
+    return success;
 }
 
 QUrl ZeiterfassungSettings::url() const
@@ -65,16 +76,25 @@ QUrl ZeiterfassungSettings::url() const
     return value(m_url, m_defaultUrl).toUrl();
 }
 
-void ZeiterfassungSettings::setUrl(const QUrl &url)
+bool ZeiterfassungSettings::setUrl(const QUrl &url)
 {
-    if(this->url() != url)
-    {
-        if(m_defaultUrl == url)
-            remove(m_url);
-        else
-            setValue(m_url, url);
+    if(this->url() == url)
+        return true;
+
+    if(m_defaultUrl == url)
+        remove(m_url);
+    else
+        setValue(m_url, url);
+
+    sync();
+
+    const auto success = status() == QSettings::NoError;
+    if(success)
         Q_EMIT urlChanged(url);
-    }
+    else
+        Q_EMIT saveErrorOccured();
+
+    return success;
 }
 
 QString ZeiterfassungSettings::username() const
@@ -82,16 +102,25 @@ QString ZeiterfassungSettings::username() const
     return value(m_username).toString();
 }
 
-void ZeiterfassungSettings::setUsername(const QString &username)
+bool ZeiterfassungSettings::setUsername(const QString &username)
 {
-    if(this->username() != username)
-    {
-        if(username.isEmpty())
-            remove(m_username);
-        else
-            setValue(m_username, username);
+    if(this->username() == username)
+        return true;
+
+    if(username.isEmpty())
+        remove(m_username);
+    else
+        setValue(m_username, username);
+
+    sync();
+
+    const auto success = status() == QSettings::NoError;
+    if(success)
         Q_EMIT usernameChanged(username);
-    }
+    else
+        Q_EMIT saveErrorOccured();
+
+    return success;
 }
 
 QString ZeiterfassungSettings::password() const
@@ -99,16 +128,25 @@ QString ZeiterfassungSettings::password() const
     return value(m_password).toString();
 }
 
-void ZeiterfassungSettings::setPassword(const QString &password)
+bool ZeiterfassungSettings::setPassword(const QString &password)
 {
-    if(this->password() != password)
-    {
-        if(password.isEmpty())
-            remove(m_password);
-        else
-            setValue(m_password, password);
+    if(this->password() == password)
+        return true;
+
+    if(password.isEmpty())
+        remove(m_password);
+    else
+        setValue(m_password, password);
+
+    sync();
+
+    const auto success = status() == QSettings::NoError;
+    if(success)
         Q_EMIT passwordChanged(password);
-    }
+    else
+        Q_EMIT saveErrorOccured();
+
+    return success;
 }
 
 QStringList ZeiterfassungSettings::projects() const
@@ -116,21 +154,30 @@ QStringList ZeiterfassungSettings::projects() const
     return value(m_projects).toStringList();
 }
 
-void ZeiterfassungSettings::setProjects(const QStringList &projects)
+bool ZeiterfassungSettings::setProjects(const QStringList &projects)
 {
-    if(this->projects() != projects)
-    {
-        if(projects.isEmpty())
-            remove(m_projects);
-        else
-            setValue(m_projects, projects);
+    if(this->projects() == projects)
+        return true;
+
+    if(projects.isEmpty())
+        remove(m_projects);
+    else
+        setValue(m_projects, projects);
+
+    sync();
+
+    const auto success = status() == QSettings::NoError;
+    if(success)
         Q_EMIT projectsChanged(projects);
-    }
+    else
+        Q_EMIT saveErrorOccured();
+
+    return success;
 }
 
-void ZeiterfassungSettings::prependProject(const QString &project)
+bool ZeiterfassungSettings::prependProject(const QString &project)
 {
-    setProjects(prependItem(projects(), project));
+    return setProjects(prependItem(projects(), project));
 }
 
 QStringList ZeiterfassungSettings::subprojects() const
@@ -138,21 +185,30 @@ QStringList ZeiterfassungSettings::subprojects() const
     return value(m_subprojects).toStringList();
 }
 
-void ZeiterfassungSettings::setSubprojects(const QStringList &subprojects)
+bool ZeiterfassungSettings::setSubprojects(const QStringList &subprojects)
 {
-    if(this->subprojects() != subprojects)
-    {
-        if(subprojects.isEmpty())
-            remove(m_subprojects);
-        else
-            setValue(m_subprojects, subprojects);
+    if(this->subprojects() == subprojects)
+        return true;
+
+    if(subprojects.isEmpty())
+        remove(m_subprojects);
+    else
+        setValue(m_subprojects, subprojects);
+
+    sync();
+
+    const auto success = status() == QSettings::NoError;
+    if(success)
         Q_EMIT subprojectsChanged(subprojects);
-    }
+    else
+        Q_EMIT saveErrorOccured();
+
+    return success;
 }
 
-void ZeiterfassungSettings::prependSubproject(const QString &subproject)
+bool ZeiterfassungSettings::prependSubproject(const QString &subproject)
 {
-    setSubprojects(prependItem(subprojects(), subproject));
+    return setSubprojects(prependItem(subprojects(), subproject));
 }
 
 QStringList ZeiterfassungSettings::workpackages() const
@@ -160,21 +216,30 @@ QStringList ZeiterfassungSettings::workpackages() const
     return value(m_workpackages).toStringList();
 }
 
-void ZeiterfassungSettings::setWorkpackages(const QStringList &workpackages)
+bool ZeiterfassungSettings::setWorkpackages(const QStringList &workpackages)
 {
-    if(this->workpackages() != workpackages)
-    {
-        if(workpackages.isEmpty())
-            remove(m_workpackages);
-        else
-            setValue(m_workpackages, workpackages);
+    if(this->workpackages() == workpackages)
+        return true;
+
+    if(workpackages.isEmpty())
+        remove(m_workpackages);
+    else
+        setValue(m_workpackages, workpackages);
+
+    sync();
+
+    const auto success = status() == QSettings::NoError;
+    if(success)
         Q_EMIT workpackagesChanged(workpackages);
-    }
+    else
+        Q_EMIT saveErrorOccured();
+
+    return success;
 }
 
-void ZeiterfassungSettings::prependWorkpackage(const QString &workpackage)
+bool ZeiterfassungSettings::prependWorkpackage(const QString &workpackage)
 {
-    setWorkpackages(prependItem(workpackages(), workpackage));
+    return setWorkpackages(prependItem(workpackages(), workpackage));
 }
 
 QStringList ZeiterfassungSettings::texts() const
@@ -182,21 +247,30 @@ QStringList ZeiterfassungSettings::texts() const
     return value(m_texts).toStringList();
 }
 
-void ZeiterfassungSettings::setTexts(const QStringList &texts)
+bool ZeiterfassungSettings::setTexts(const QStringList &texts)
 {
-    if(this->texts() != texts)
-    {
-        if(m_texts.isEmpty())
-            remove(m_texts);
-        else
-            setValue(m_texts, texts);
+    if(this->texts() == texts)
+        return true;
+
+    if(m_texts.isEmpty())
+        remove(m_texts);
+    else
+        setValue(m_texts, texts);
+
+    sync();
+
+    const auto success = status() == QSettings::NoError;
+    if(success)
         Q_EMIT textsChanged(texts);
-    }
+    else
+        Q_EMIT saveErrorOccured();
+
+    return success;
 }
 
-void ZeiterfassungSettings::prependText(const QString &text)
+bool ZeiterfassungSettings::prependText(const QString &text)
 {
-    setTexts(prependItem(texts(), text));
+    return setTexts(prependItem(texts(), text));
 }
 
 QString ZeiterfassungSettings::theme() const
@@ -204,16 +278,25 @@ QString ZeiterfassungSettings::theme() const
     return value(m_theme).toString();
 }
 
-void ZeiterfassungSettings::setTheme(const QString &theme)
+bool ZeiterfassungSettings::setTheme(const QString &theme)
 {
-    if(this->theme() != theme)
-    {
-        if(theme.isEmpty())
-            remove(m_theme);
-        else
-            setValue(m_theme, theme);
+    if(this->theme() == theme)
+        return true;
+
+    if(theme.isEmpty())
+        remove(m_theme);
+    else
+        setValue(m_theme, theme);
+
+    sync();
+
+    const auto success = status() == QSettings::NoError;
+    if(success)
         Q_EMIT themeChanged(theme);
-    }
+    else
+        Q_EMIT saveErrorOccured();
+
+    return success;
 }
 
 QStringList ZeiterfassungSettings::prependItem(QStringList list, const QString &item)
diff --git a/zeiterfassungcorelib/zeiterfassungsettings.h b/zeiterfassungcorelib/zeiterfassungsettings.h
index 8b35a75..c1f80e4 100644
--- a/zeiterfassungcorelib/zeiterfassungsettings.h
+++ b/zeiterfassungcorelib/zeiterfassungsettings.h
@@ -33,37 +33,39 @@ public:
     explicit ZeiterfassungSettings(QObject *parent = Q_NULLPTR);
 
     QLocale::Language language() const;
-    void setLanguage(QLocale::Language language);
+    bool setLanguage(QLocale::Language language);
 
     QUrl url() const;
-    void setUrl(const QUrl &url);
+    bool setUrl(const QUrl &url);
 
     QString username() const;
-    void setUsername(const QString &username);
+    bool setUsername(const QString &username);
 
     QString password() const;
-    void setPassword(const QString &password);
+    bool setPassword(const QString &password);
 
     QStringList projects() const;
-    void setProjects(const QStringList &projects);
-    void prependProject(const QString &project);
+    bool setProjects(const QStringList &projects);
+    bool prependProject(const QString &project);
 
     QStringList subprojects() const;
-    void setSubprojects(const QStringList &subprojects);
-    void prependSubproject(const QString &subproject);
+    bool setSubprojects(const QStringList &subprojects);
+    bool prependSubproject(const QString &subproject);
 
     QStringList workpackages() const;
-    void setWorkpackages(const QStringList &workpackages);
-    void prependWorkpackage(const QString &workpackage);
+    bool setWorkpackages(const QStringList &workpackages);
+    bool prependWorkpackage(const QString &workpackage);
 
     QStringList texts() const;
-    void setTexts(const QStringList &texts);
-    void prependText(const QString &text);
+    bool setTexts(const QStringList &texts);
+    bool prependText(const QString &text);
 
     QString theme() const;
-    void setTheme(const QString &theme);
+    bool setTheme(const QString &theme);
 
 Q_SIGNALS:
+    void saveErrorOccured();
+
     void languageChanged(QLocale::Language language);
     void urlChanged(const QUrl &url);
     void usernameChanged(const QString &username);
diff --git a/zeiterfassungguilib/dialogs/settingsdialog.cpp b/zeiterfassungguilib/dialogs/settingsdialog.cpp
index 2e2c315..c1a41e9 100644
--- a/zeiterfassungguilib/dialogs/settingsdialog.cpp
+++ b/zeiterfassungguilib/dialogs/settingsdialog.cpp
@@ -82,7 +82,12 @@ void SettingsDialog::submit()
 
     if(ui->comboBoxLanguage->currentData().value<QLocale::Language>() != m_settings.language())
     {
-        m_settings.setLanguage(ui->comboBoxLanguage->currentData().value<QLocale::Language>());
+        if(!m_settings.setLanguage(ui->comboBoxLanguage->currentData().value<QLocale::Language>()))
+        {
+            errorOccured();
+            return;
+        }
+
         //TODO #73 Allow changing of the language without restart
         QMessageBox::information(this, tr("Restart required!"), tr("To apply the new settings a restart is required!"));
     }
@@ -90,9 +95,8 @@ void SettingsDialog::submit()
     auto theme = ui->comboBoxTheme->currentData().toString();
     if(theme != m_settings.theme())
     {
-        if(theme.isEmpty())
-            qApp->setStyleSheet(QString());
-        else
+        QString styleSheet;
+        if(!theme.isEmpty())
         {
             auto themePath = QDir(QDir(QCoreApplication::applicationDirPath()).absoluteFilePath(QStringLiteral("themes"))).absoluteFilePath(theme);
 
@@ -111,14 +115,31 @@ void SettingsDialog::submit()
             }
 
             QTextStream textStream(&file);
-            qApp->setStyleSheet(textStream.readAll().replace(QStringLiteral("@THEME_RESOURCES@"), themePath));
+            styleSheet = textStream.readAll().replace(QStringLiteral("@THEME_RESOURCES@"), themePath);
         }
 
-        m_settings.setTheme(theme);
+        if(!m_settings.setTheme(theme))
+        {
+            errorOccured();
+            return;
+        }
+
+        qApp->setStyleSheet(styleSheet);
     }
 
     for(const auto widget : m_settingsWidgets)
-        widget->apply();
+    {
+        if(!widget->apply())
+        {
+            errorOccured();
+            return;
+        }
+    }
 
     accept();
 }
+
+void SettingsDialog::errorOccured()
+{
+    QMessageBox::warning(this, tr("Could not save settings!"), tr("Could not load settings!") % "\n\n" % tr("Make sure you have writing permissions!"));
+}
diff --git a/zeiterfassungguilib/dialogs/settingsdialog.h b/zeiterfassungguilib/dialogs/settingsdialog.h
index 149869d..cd567d2 100644
--- a/zeiterfassungguilib/dialogs/settingsdialog.h
+++ b/zeiterfassungguilib/dialogs/settingsdialog.h
@@ -20,6 +20,8 @@ private Q_SLOTS:
     void submit();
 
 private:
+    void errorOccured();
+
     Ui::SettingsDialog *ui;
     ZeiterfassungSettings &m_settings;
     QVector<SettingsWidget*> m_settingsWidgets;
diff --git a/zeiterfassungguilib/settingswidget.h b/zeiterfassungguilib/settingswidget.h
index 7b21ff2..65aebee 100644
--- a/zeiterfassungguilib/settingswidget.h
+++ b/zeiterfassungguilib/settingswidget.h
@@ -15,5 +15,5 @@ public:
     virtual bool isValid(QString &message) const { Q_UNUSED(message) return true; }
 
 public Q_SLOTS:
-    virtual void apply() { }
+    virtual bool apply() = 0;
 };