diff --git a/ui_close_dialog.py b/ui_close_dialog.py
deleted file mode 100644
index 52c2187..0000000
--- a/ui_close_dialog.py
+++ /dev/null
@@ -1,52 +0,0 @@
-# -*- coding: utf-8 -*-
-
-# Form implementation generated from reading ui file 'ui_close_dialog.ui'
-#
-# Created by: PyQt5 UI code generator 5.15.0
-#
-# WARNING: Any manual changes made to this file will be lost when pyuic5 is
-# run again.  Do not edit this file unless you know what you are doing.
-
-
-from PyQt5 import QtCore, QtGui, QtWidgets
-
-
-class Ui_CloseDialog(object):
-    def setupUi(self, CloseDialog):
-        CloseDialog.setObjectName("CloseDialog")
-        CloseDialog.setWindowModality(QtCore.Qt.ApplicationModal)
-        CloseDialog.resize(313, 75)
-        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Maximum, QtWidgets.QSizePolicy.Minimum)
-        sizePolicy.setHorizontalStretch(0)
-        sizePolicy.setVerticalStretch(0)
-        sizePolicy.setHeightForWidth(CloseDialog.sizePolicy().hasHeightForWidth())
-        CloseDialog.setSizePolicy(sizePolicy)
-        self.verticalLayout = QtWidgets.QVBoxLayout(CloseDialog)
-        self.verticalLayout.setObjectName("verticalLayout")
-        self.t_close = QtWidgets.QLabel(CloseDialog)
-        self.t_close.setObjectName("t_close")
-        self.verticalLayout.addWidget(self.t_close)
-        self.l_buttons = QtWidgets.QHBoxLayout()
-        self.l_buttons.setObjectName("l_buttons")
-        self.b_yes = QtWidgets.QPushButton(CloseDialog)
-        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Minimum, QtWidgets.QSizePolicy.Minimum)
-        sizePolicy.setHorizontalStretch(0)
-        sizePolicy.setVerticalStretch(0)
-        sizePolicy.setHeightForWidth(self.b_yes.sizePolicy().hasHeightForWidth())
-        self.b_yes.setSizePolicy(sizePolicy)
-        self.b_yes.setObjectName("b_yes")
-        self.l_buttons.addWidget(self.b_yes)
-        self.b_no = QtWidgets.QPushButton(CloseDialog)
-        self.b_no.setObjectName("b_no")
-        self.l_buttons.addWidget(self.b_no)
-        self.verticalLayout.addLayout(self.l_buttons)
-
-        self.retranslateUi(CloseDialog)
-        QtCore.QMetaObject.connectSlotsByName(CloseDialog)
-
-    def retranslateUi(self, CloseDialog):
-        _translate = QtCore.QCoreApplication.translate
-        CloseDialog.setWindowTitle(_translate("CloseDialog", "Programm schließen"))
-        self.t_close.setText(_translate("CloseDialog", "Soll das Programm wirklich geschlossen werden?"))
-        self.b_yes.setText(_translate("CloseDialog", "Ja"))
-        self.b_no.setText(_translate("CloseDialog", "Nein"))
diff --git a/ui_close_dialog.ui b/ui_close_dialog.ui
deleted file mode 100644
index e28c378..0000000
--- a/ui_close_dialog.ui
+++ /dev/null
@@ -1,61 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<ui version="4.0">
- <class>CloseDialog</class>
- <widget class="QDialog" name="CloseDialog">
-  <property name="windowModality">
-   <enum>Qt::ApplicationModal</enum>
-  </property>
-  <property name="geometry">
-   <rect>
-    <x>0</x>
-    <y>0</y>
-    <width>313</width>
-    <height>75</height>
-   </rect>
-  </property>
-  <property name="sizePolicy">
-   <sizepolicy hsizetype="Maximum" vsizetype="Minimum">
-    <horstretch>0</horstretch>
-    <verstretch>0</verstretch>
-   </sizepolicy>
-  </property>
-  <property name="windowTitle">
-   <string>Programm schließen</string>
-  </property>
-  <layout class="QVBoxLayout" name="verticalLayout">
-   <item>
-    <widget class="QLabel" name="t_close">
-     <property name="text">
-      <string>Soll das Programm wirklich geschlossen werden?</string>
-     </property>
-    </widget>
-   </item>
-   <item>
-    <layout class="QHBoxLayout" name="l_buttons">
-     <item>
-      <widget class="QPushButton" name="b_yes">
-       <property name="sizePolicy">
-        <sizepolicy hsizetype="Minimum" vsizetype="Minimum">
-         <horstretch>0</horstretch>
-         <verstretch>0</verstretch>
-        </sizepolicy>
-       </property>
-       <property name="text">
-        <string>Ja</string>
-       </property>
-      </widget>
-     </item>
-     <item>
-      <widget class="QPushButton" name="b_no">
-       <property name="text">
-        <string>Nein</string>
-       </property>
-      </widget>
-     </item>
-    </layout>
-   </item>
-  </layout>
- </widget>
- <resources/>
- <connections/>
-</ui>
diff --git a/wikicookbook.py b/wikicookbook.py
index 86ce9c2..74e7def 100644
--- a/wikicookbook.py
+++ b/wikicookbook.py
@@ -29,7 +29,6 @@ from ui_mainwindow import Ui_MainWindow
 from ui_code_dialog import Ui_WikiCode
 from ui_about_dialog import Ui_About
 from ui_clear_dialog import Ui_ClearDialog
-from ui_close_dialog import Ui_CloseDialog
 
 class AboutDialog(QDialog, Ui_About):
     def __init__(self, *args, **kwargs):
@@ -40,16 +39,6 @@ class AboutDialog(QDialog, Ui_About):
 
         self.show()
 
-class CloseDialog(QDialog, Ui_CloseDialog):
-    def __init__(self, *args, **kwargs):
-        super(CloseDialog, self).__init__(*args, **kwargs)
-        self.setupUi(self)
-
-        self.b_yes.clicked.connect(self.accept)
-        self.b_no.clicked.connect(self.reject)
-
-        self.show()
-
 class ClearDialog(QDialog, Ui_ClearDialog):
     def __init__(self, *args, **kwargs):
         super(ClearDialog, self).__init__(*args, **kwargs)
@@ -397,9 +386,11 @@ class MainWindow(QMainWindow, Ui_MainWindow):
         """
         Close the application. A warning is shown before.
         """
-        dialog = CloseDialog()
-        dialog.accepted.connect(self.close)
-        dialog.exec_()
+        reply = QMessageBox.question(self, "Sicher?",
+            "Möchten Sie wirklich schließen?",
+            QMessageBox.Yes | QMessageBox.No, QMessageBox.No)
+        if reply == QMessageBox.Yes:
+            self.close()
 
 
 if __name__ == "__main__":