diff --git a/qucs-activefilter/CMakeLists.txt b/qucs-activefilter/CMakeLists.txt
index e53d8010..455027f4 100644
--- a/qucs-activefilter/CMakeLists.txt
+++ b/qucs-activefilter/CMakeLists.txt
@@ -35,11 +35,18 @@ CONFIGURE_FILE (
 
 INCLUDE_DIRECTORIES("${PROJECT_BINARY_DIR}")
 
-FIND_PACKAGE( Qt4 REQUIRED )
-SET( QT_USE_QTGUI TRUE )
-SET( QT_USE_QTSVG TRUE )
+FIND_PACKAGE( Qt5 COMPONENTS Core Gui Widgets Svg REQUIRED)
+#INCLUDE( ${QT_USE_FILE} )
+
+INCLUDE_DIRECTORIES(
+      ${Qt5Core_INCLUDE_DIRS}
+      ${Qt5Widgets_INCLUDE_DIRS}
+      ${Qt5Svg_INCLUDE_DIRS}
+      )
+
+# bug, the find package does not seem to set the QT_LIBRARIES, do it manually
+SET(QT_LIBRARIES  ${Qt5Core_LIBRARIES} ${Qt5Widgets_LIBRARIES} ${Qt5Svg_LIBRARIES}  )
 
-INCLUDE( ${QT_USE_FILE} )
 
 ADD_DEFINITIONS(${QT_DEFINITIONS})
 
@@ -61,10 +68,10 @@ qucsactivefilter.h
 helpdialog.h
 )
 
-QT4_WRAP_CPP(QUCS-ACTIVE-FILTER_MOC_SRCS ${QUCS-ACTIVE-FILTER_MOC_HDRS})
+QT5_WRAP_CPP(QUCS-ACTIVE-FILTER_MOC_SRCS ${QUCS-ACTIVE-FILTER_MOC_HDRS})
 
 SET(RESOURCES qucsactivefilter.qrc)
-QT4_ADD_RESOURCES(RESOURCES_SRCS ${RESOURCES})
+QT5_ADD_RESOURCES(RESOURCES_SRCS ${RESOURCES})
 
 
 IF(APPLE)
diff --git a/qucs-activefilter/qucsactivefilter.cpp b/qucs-activefilter/qucsactivefilter.cpp
index 69be24b7..89b66801 100644
--- a/qucs-activefilter/qucsactivefilter.cpp
+++ b/qucs-activefilter/qucsactivefilter.cpp
@@ -41,14 +41,14 @@ QucsActiveFilter::QucsActiveFilter(QWidget *parent)
     setWindowIcon(QPixmap(":/images/bitmaps/big.qucs.xpm"));
     setWindowTitle("Qucs Active Filter " PACKAGE_VERSION);
 
-    QTextCodec::setCodecForTr(QTextCodec::codecForName("UTF-8"));
+    //QTextCodec::setCodecForTr(QTextCodec::codecForName("UTF-8"));
 
     // --------  create menubar  -------------------
     QMenu *fileMenu = new QMenu(tr("&File"));
 
     QAction * fileQuit = new QAction(tr("E&xit"), this);
     fileQuit->setShortcut(Qt::CTRL+Qt::Key_Q);
-    connect(fileQuit, SIGNAL(activated()), SLOT(close()));
+    connect(fileQuit, SIGNAL(triggered(bool)), SLOT(close()));
 
     fileMenu->addAction(fileQuit);
 
@@ -66,15 +66,15 @@ QucsActiveFilter::QucsActiveFilter(QWidget *parent)
     QMenu *helpMenu = new QMenu(tr("&Help"), this);
     QAction * helpHelp = new QAction(tr("Help..."), this);
     helpHelp->setShortcut(Qt::Key_F1);
-    connect(helpHelp, SIGNAL(activated()), SLOT(slotHelpIntro()));
+    connect(helpHelp, SIGNAL(triggered(bool)), SLOT(slotHelpIntro()));
 
     QAction * helpAbout = new QAction(tr("&About QucsActiveFilter..."), this);
     helpMenu->addAction(helpAbout);
-    connect(helpAbout, SIGNAL(activated()), SLOT(slotHelpAbout()));
+    connect(helpAbout, SIGNAL(triggered(bool)), SLOT(slotHelpAbout()));
 
     QAction * helpAboutQt = new QAction(tr("About Qt..."), this);
     helpMenu->addAction(helpAboutQt);
-    connect(helpAboutQt, SIGNAL(activated()), SLOT(slotHelpAboutQt()));
+    connect(helpAboutQt, SIGNAL(triggered(bool)), SLOT(slotHelpAboutQt()));
 
     helpMenu->addAction(helpHelp);
     helpMenu->addSeparator();
diff --git a/qucs-activefilter/transferfuncdialog.h b/qucs-activefilter/transferfuncdialog.h
index 6410815d..fca5db24 100644
--- a/qucs-activefilter/transferfuncdialog.h
+++ b/qucs-activefilter/transferfuncdialog.h
@@ -18,8 +18,8 @@
 #ifndef TRANSFERFUNCDIALOG_H
 #define TRANSFERFUNCDIALOG_H
 
-#include <QWidget>
 #include <QtGui>
+#include <QtWidgets>
 
 class TransferFuncDialog : public QDialog
 {