diff --git a/src/core/core.cpp b/src/core/core.cpp
index 0a62a00f6..be00452bc 100644
--- a/src/core/core.cpp
+++ b/src/core/core.cpp
@@ -94,10 +94,13 @@ Core::~Core()
                                       Q_ARG(bool, false));
     }
     coreThread->exit(0);
-    while (coreThread->isRunning())
+    if (QThread::currentThread() != coreThread)
     {
-        qApp->processEvents();
-        coreThread->wait(500);
+        while (coreThread->isRunning())
+        {
+            qApp->processEvents();
+            coreThread->wait(500);
+        }
     }
 
     deadifyTox();
diff --git a/src/ipc.cpp b/src/ipc.cpp
index 7895b129b..630db31ac 100644
--- a/src/ipc.cpp
+++ b/src/ipc.cpp
@@ -175,6 +175,10 @@ bool IPC::isCurrentOwner()
     }
 }
 
+/**
+ * @brief Register a handler for an IPC event
+ * @param handler The handler callback. Should not block for more than a second, at worst
+ */
 void IPC::registerEventHandler(const QString &name, IPCEventHandler handler)
 {
     eventHandlers[name] = handler;
diff --git a/src/main.cpp b/src/main.cpp
index f9898bdeb..bc6dbe892 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -295,7 +295,8 @@ int main(int argc, char *argv[])
         }
     }
 
-    Nexus::getInstance().start();
+    Nexus& nexus = Nexus::getInstance();
+    nexus.start();
 
     // Event was not handled by already running instance therefore we handle it ourselves
     if (eventType == "uri")
@@ -303,8 +304,10 @@ int main(int argc, char *argv[])
     else if (eventType == "save")
         handleToxSave(firstParam.toUtf8());
 
-    // Run
-    int errorcode = a.exec();
+    // Run (unless we already quit before starting!)
+    int errorcode = 0;
+    if (nexus.isRunning())
+        errorcode = a.exec();
 
     Nexus::destroyInstance();
     CameraSource::destroyInstance();
diff --git a/src/net/toxuri.cpp b/src/net/toxuri.cpp
index b4a1154ac..c91f96066 100644
--- a/src/net/toxuri.cpp
+++ b/src/net/toxuri.cpp
@@ -51,16 +51,25 @@ bool toxURIEventHandler(const QByteArray& eventData)
  */
 bool handleToxURI(const QString &toxURI)
 {
-    Core* core = Core::getInstance();
+    Nexus& nexus = Nexus::getInstance();
+    Core* core = nexus.getCore();
 
     while (!core)
     {
-        core = Core::getInstance();
+        if (!nexus.isRunning())
+            return false;
+
+        core = nexus.getCore();
         qApp->processEvents();
     }
 
     while (!core->isReady())
+    {
+        if (!nexus.isRunning())
+            return false;
+
         qApp->processEvents();
+    }
 
     QString toxaddr = toxURI.mid(4);
 
@@ -70,18 +79,26 @@ bool handleToxURI(const QString &toxURI)
         toxId = Toxme::lookup(toxaddr);
         if (!toxId.isValid())
         {
-            QMessageBox::warning(0, "qTox",
-                                         ToxURIDialog::tr("%1 is not a valid Toxme address.")
-                                         .arg(toxaddr));
+            QMessageBox *messageBox = new QMessageBox(QMessageBox::Warning, "qTox",
+                                   QMessageBox::tr("%1 is not a valid Toxme address.")
+                                   .arg(toxaddr), QMessageBox::Ok, nullptr);
+            messageBox->setButtonText(QMessageBox::Ok, QMessageBox::tr("Ok"));
+            QObject::connect(messageBox, &QMessageBox::finished, messageBox, &QMessageBox::deleteLater);
+            messageBox->show();
             return false;
         }
     }
 
-    ToxURIDialog dialog(0, toxaddr, QObject::tr("%1 here! Tox me maybe?",
+    ToxURIDialog *dialog = new ToxURIDialog(0, toxaddr, QObject::tr("%1 here! Tox me maybe?",
                                                 "Default message in Tox URI friend requests. Write something appropriate!")
                         .arg(Nexus::getCore()->getUsername()));
-    if (dialog.exec() == QDialog::Accepted)
-        Core::getInstance()->requestFriendship(toxId, dialog.getRequestMessage());
+    QObject::connect(dialog, &ToxURIDialog::finished, [=](int result) {
+        if (result == QDialog::Accepted)
+                Core::getInstance()->requestFriendship(toxId, dialog->getRequestMessage());
+
+        dialog->deleteLater();
+    });
+    dialog->open();
 
     return true;
 }
diff --git a/src/nexus.cpp b/src/nexus.cpp
index b08762ed5..20a330be8 100644
--- a/src/nexus.cpp
+++ b/src/nexus.cpp
@@ -59,15 +59,20 @@ Nexus::Nexus(QObject *parent) :
     QObject(parent),
     profile{nullptr},
     widget{nullptr},
-    loginScreen{nullptr}
+    loginScreen{nullptr},
+    running{true},
+    quitOnLastWindowClosed{true}
 {
 }
 
 Nexus::~Nexus()
 {
     delete widget;
+    widget = nullptr;
     delete loginScreen;
+    loginScreen = nullptr;
     delete profile;
+    profile = nullptr;
     Settings::getInstance().saveGlobal();
 #ifdef Q_OS_MAC
     delete globalMenuBar;
@@ -104,6 +109,14 @@ void Nexus::start()
 
     loginScreen = new LoginScreen();
 
+    // We need this LastWindowClosed dance because the LoginScreen may be shown
+    // and closed in a processEvents() loop before the start of the real
+    // exec() event loop, meaning we wouldn't receive the onLastWindowClosed,
+    // and so we wouldn't have a chance to tell the processEvents() loop to quit.
+    qApp->setQuitOnLastWindowClosed(false);
+    connect(qApp, &QApplication::lastWindowClosed, this, &Nexus::onLastWindowClosed);
+    connect(loginScreen, &LoginScreen::closed, this, &Nexus::onLastWindowClosed);
+
 #ifdef Q_OS_MAC
     globalMenuBar = new QMenuBar(0);
     dockMenu = new QMenu(globalMenuBar);
@@ -161,14 +174,14 @@ void Nexus::showLogin()
     loginScreen->reset();
     loginScreen->move(QApplication::desktop()->screen()->rect().center() - loginScreen->rect().center());
     loginScreen->show();
-    ((QApplication*)qApp)->setQuitOnLastWindowClosed(true);
+    quitOnLastWindowClosed = true;
 }
 
 void Nexus::showMainGUI()
 {
     assert(profile);
 
-    ((QApplication*)qApp)->setQuitOnLastWindowClosed(false);
+    quitOnLastWindowClosed = false;
     loginScreen->close();
 
     // Create GUI
@@ -220,6 +233,26 @@ void Nexus::showMainGUI()
     profile->startCore();
 }
 
+/**
+ * @brief Calls QApplication::quit(), and causes Nexus::isRunning() to return false
+ */
+void Nexus::quit()
+{
+    running = false;
+    qApp->quit();
+}
+
+/**
+ * @brief Returns true until Nexus::quit is called.
+ *
+ * Any blocking processEvents() loop should check this as a return condition,
+ * since the application can not quit until control is returned to the event loop.
+ */
+bool Nexus::isRunning()
+{
+    return running;
+}
+
 /**
  * @brief Returns the singleton instance.
  */
@@ -310,6 +343,12 @@ void Nexus::showLoginLater()
     QMetaObject::invokeMethod(&getInstance(), "showLogin", Qt::QueuedConnection);
 }
 
+void Nexus::onLastWindowClosed()
+{
+    if (quitOnLastWindowClosed)
+        quit();
+}
+
 #ifdef Q_OS_MAC
 void Nexus::retranslateUi()
 {
diff --git a/src/nexus.h b/src/nexus.h
index 080482f39..97437719b 100644
--- a/src/nexus.h
+++ b/src/nexus.h
@@ -43,6 +43,8 @@ class Nexus : public QObject
 public:
     void start();
     void showMainGUI();
+    void quit();
+    bool isRunning();
 
     static Nexus& getInstance();
     static void destroyInstance();
@@ -84,6 +86,9 @@ private:
     QActionGroup* windowActions = nullptr;
 #endif
 
+private slots:
+    void onLastWindowClosed();
+
 private:
     explicit Nexus(QObject *parent = 0);
     ~Nexus();
@@ -92,6 +97,8 @@ private:
     Profile* profile;
     Widget* widget;
     LoginScreen* loginScreen;
+    bool running;
+    bool quitOnLastWindowClosed;
 };
 
 #endif // NEXUS_H
diff --git a/src/persistence/profile.cpp b/src/persistence/profile.cpp
index 763a39e6b..74ec53a7b 100644
--- a/src/persistence/profile.cpp
+++ b/src/persistence/profile.cpp
@@ -211,7 +211,10 @@ Profile::~Profile()
         saveToxSave();
     }
 
-    delete core;
+    core->deleteLater();
+    while (coreThread->isRunning())
+        qApp->processEvents();
+
     delete coreThread;
     if (!isRemoved)
     {
diff --git a/src/widget/gui.cpp b/src/widget/gui.cpp
index f8cdd4296..21274e827 100644
--- a/src/widget/gui.cpp
+++ b/src/widget/gui.cpp
@@ -322,25 +322,34 @@ QString GUI::passwordDialog(const QString& cancel, const QString& body)
 
 void GUI::_clearContacts()
 {
-    Nexus::getDesktopGUI()->clearContactsList();
+    Widget* w = Nexus::getDesktopGUI();
+    if (w)
+        w->clearContactsList();
 }
 
 void GUI::_setEnabled(bool state)
 {
-    Nexus::getDesktopGUI()->setEnabled(state);
+    Widget* w = Nexus::getDesktopGUI();
+    if (w)
+        w->setEnabled(state);
 }
 
 void GUI::_setWindowTitle(const QString& title)
 {
+    QWidget* w = getMainWidget();
+    if (!w)
+        return;
     if (title.isEmpty())
-        getMainWidget()->setWindowTitle("qTox");
+        w->setWindowTitle("qTox");
     else
-        getMainWidget()->setWindowTitle("qTox - " + title);
+        w->setWindowTitle("qTox - " + title);
 }
 
 void GUI::_reloadTheme()
 {
-    Nexus::getDesktopGUI()->reloadTheme();
+    Widget* w = Nexus::getDesktopGUI();
+    if (w)
+        w->reloadTheme();
 }
 
 void GUI::_showInfo(const QString& title, const QString& msg)
@@ -366,7 +375,9 @@ void GUI::_showError(const QString& title, const QString& msg)
 
 void GUI::_showUpdateDownloadProgress()
 {
-    Nexus::getDesktopGUI()->showUpdateDownloadProgress();
+    Widget* w = Nexus::getDesktopGUI();
+    if (w)
+        w->showUpdateDownloadProgress();
 }
 
 bool GUI::_askQuestion(const QString& title, const QString& msg,
diff --git a/src/widget/loginscreen.cpp b/src/widget/loginscreen.cpp
index 24dfb0c84..0ad34a07c 100644
--- a/src/widget/loginscreen.cpp
+++ b/src/widget/loginscreen.cpp
@@ -126,6 +126,11 @@ bool LoginScreen::event(QEvent* event)
     return QWidget::event(event);
 }
 
+void LoginScreen::closeEvent(QCloseEvent*)
+{
+    emit closed();
+}
+
 void LoginScreen::onNewProfilePageClicked()
 {
     ui->stackedWidget->setCurrentIndex(0);
diff --git a/src/widget/loginscreen.h b/src/widget/loginscreen.h
index fdf223480..82441842c 100644
--- a/src/widget/loginscreen.h
+++ b/src/widget/loginscreen.h
@@ -42,6 +42,10 @@ public:
 
 signals:
     void windowStateChanged(Qt::WindowStates states);
+    void closed();
+
+protected:
+    virtual void closeEvent(QCloseEvent *event) final override;
 
 private slots:
     void onAutoLoginToggled(int state);
diff --git a/src/widget/widget.cpp b/src/widget/widget.cpp
index 632b5a17e..cdaef7191 100644
--- a/src/widget/widget.cpp
+++ b/src/widget/widget.cpp
@@ -594,7 +594,7 @@ void Widget::closeEvent(QCloseEvent *event)
         saveWindowGeometry();
         saveSplitterGeometry();
         QWidget::closeEvent(event);
-        qApp->quit();
+        Nexus::getInstance().quit();
     }
 }
 
@@ -647,7 +647,7 @@ void Widget::onFailedToStartCore()
     critical.setText(tr("toxcore failed to start, the application will terminate after you close this message."));
     critical.setIcon(QMessageBox::Critical);
     critical.exec();
-    qApp->quit();
+    Nexus::getInstance().quit();
 }
 
 void Widget::onBadProxyCore()