diff --git a/src/gui/MainWindow.h b/src/gui/MainWindow.h
index eb677fbb..4435c13b 100644
--- a/src/gui/MainWindow.h
+++ b/src/gui/MainWindow.h
@@ -109,6 +109,7 @@ private:
     bool appExitCalled;
 };
 
-#define KEEPASSXC_MAIN_WINDOW qobject_cast<MainWindow*>(qobject_cast<Application*>(qApp)->mainWindow())
+#define KEEPASSXC_MAIN_WINDOW (qobject_cast<Application*>(qApp) ? \
+                               qobject_cast<MainWindow*>(qobject_cast<Application*>(qApp)->mainWindow()) : nullptr)
 
 #endif // KEEPASSX_MAINWINDOW_H
diff --git a/src/keys/YkChallengeResponseKey.cpp b/src/keys/YkChallengeResponseKey.cpp
index 60db4282..dcd58335 100644
--- a/src/keys/YkChallengeResponseKey.cpp
+++ b/src/keys/YkChallengeResponseKey.cpp
@@ -33,8 +33,10 @@ YkChallengeResponseKey::YkChallengeResponseKey(int slot, bool blocking)
     : m_slot(slot),
       m_blocking(blocking)
 {
-    connect(this, SIGNAL(userInteractionRequired()), KEEPASSXC_MAIN_WINDOW, SLOT(showYubiKeyPopup()));
-    connect(this, SIGNAL(userConfirmed()), KEEPASSXC_MAIN_WINDOW, SLOT(hideYubiKeyPopup()));
+    if (KEEPASSXC_MAIN_WINDOW) {
+        connect(this, SIGNAL(userInteractionRequired()), KEEPASSXC_MAIN_WINDOW, SLOT(showYubiKeyPopup()));
+        connect(this, SIGNAL(userConfirmed()), KEEPASSXC_MAIN_WINDOW, SLOT(hideYubiKeyPopup()));
+    }
 }
 
 QByteArray YkChallengeResponseKey::rawKey() const