diff --git a/src/ctrl.cpp b/src/ctrl.cpp
index ea5121f..02ac802 100644
--- a/src/ctrl.cpp
+++ b/src/ctrl.cpp
@@ -23,7 +23,7 @@
  */
 
 
-#include <QtGui>
+#include <QtWidgets>
 #include <time.h>
 #include <math.h>
 
diff --git a/src/gui.cpp b/src/gui.cpp
index 7c05716..76f02d0 100644
--- a/src/gui.cpp
+++ b/src/gui.cpp
@@ -23,7 +23,7 @@
  */
 
 
-#include <QtGui>
+#include <QtWidgets>
 #include <qwt_plot.h>
 #include <qwt_plot_curve.h>
 #include <SFMT.h>
diff --git a/src/paint.cpp b/src/paint.cpp
index ab42cec..ce36227 100644
--- a/src/paint.cpp
+++ b/src/paint.cpp
@@ -204,6 +204,8 @@ NernstPainter::resetPaint()
 void
 NernstPainter::initializeGL()
 {
+   initializeOpenGLFunctions();
+
    qglClearColor( Qt::white );
    glShadeModel( GL_FLAT );
    glEnable( GL_DEPTH_TEST );
diff --git a/src/paint.h b/src/paint.h
index 76adfa6..5c0d8c7 100644
--- a/src/paint.h
+++ b/src/paint.h
@@ -27,9 +27,10 @@
 
 
 #include <QGLWidget>
+#include <QOpenGLFunctions_1_1>
 
 
-class NernstPainter : public QGLWidget
+class NernstPainter : public QGLWidget, public QOpenGLFunctions_1_1
 {
    Q_OBJECT
 
diff --git a/src/status.cpp b/src/status.cpp
index e9ba182..ab47e80 100644
--- a/src/status.cpp
+++ b/src/status.cpp
@@ -23,7 +23,7 @@
  */
 
 
-#include <QtGui>
+#include <QtWidgets>
 
 #include "status.h"
 #include "gui.h"