diff --git a/CMakeLists.txt b/CMakeLists.txt
index e76a9eca336049737edb69ae8a523e3549c20905..425ad59dddd53cf0603aa43b63bd7889db10a4b1 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,7 +1,5 @@
 include(plugin)
 
-find_package(Qwt5)
-
 if (EXISTS ${CMAKE_SOURCE_DIR}/ObjectTypes/PolyhedralMesh)
     add_definitions (-DENABLE_OPENVOLUMEMESH_SUPPORT)
     add_definitions (-DENABLE_OPENVOLUMEMESH_POLYHEDRAL_SUPPORT)
@@ -12,19 +10,23 @@ if (EXISTS ${CMAKE_SOURCE_DIR}/ObjectTypes/HexahedralMesh)
     add_definitions (-DENABLE_OPENVOLUMEMESH_HEXAHEDRAL_SUPPORT)
 endif()
 
-if(Qwt5_Qt4_FOUND)
-  add_definitions(-DWITH_QWT)
-  openflipper_plugin(INCDIRS ${Qwt5_INCLUDE_DIR} LIBRARIES ${Qwt5_Qt4_LIBRARY})
+# use Qwt6 for QT5
+if (NOT FORCE_QT4 AND QT5_FOUND)
+  find_package(Qwt6)
+
+  if (QWT6_FOUND)
+    add_definitions(-DWITH_QWT)
+    openflipper_plugin(INCDIRS ${QWT6_INCLUDE_DIRS} LIBRARIES ${QWT6_LIBRARIES})
+  else()
+    openflipper_plugin()
+  endif()
 else()
-  openflipper_plugin()
+  find_package(Qwt5)
+
+  if(Qwt5_Qt4_FOUND)
+    add_definitions(-DWITH_QWT)
+    openflipper_plugin(INCDIRS ${Qwt5_INCLUDE_DIR} LIBRARIES ${Qwt5_Qt4_LIBRARY})
+  else()
+    openflipper_plugin()
+  endif()
 endif()
-
-
-
-
-
-
-
-
-
-
diff --git a/QwtFunctionPlot.hh b/QwtFunctionPlot.hh
index 8ae08403de66d596bebde6ebc542990a87db7790..9585ee73bc9a46edf2d08be7727f1f5fdbf4efed 100644
--- a/QwtFunctionPlot.hh
+++ b/QwtFunctionPlot.hh
@@ -72,6 +72,8 @@
 #include <qwt_scale_engine.h>
 #include <qwt_plot_marker.h>
 
+#include <QDialog>
+
 // qmake users have to include pc
 #include <ui_QwtFunctionPlotBase.hh>