diff --git a/GUI/View/Common/DataItemBundleWidget.cpp b/GUI/View/Common/DataItemBundleWidget.cpp
index 2f47c0663e171998dc1adc63edd146ef40ffcb98..b5e024738ad2cc22ebf9eec08d63343d8e5c0b0d 100644
--- a/GUI/View/Common/DataItemBundleWidget.cpp
+++ b/GUI/View/Common/DataItemBundleWidget.cpp
@@ -13,6 +13,8 @@
 //  ************************************************************************************************
 
 #include "GUI/View/Common/DataItemBundleWidget.h"
+#include "GUI/Model/Data/IntensityDataItem.h"
+#include "GUI/Model/Data/SpecularDataItem.h"
 
 DataItemBundleWidget::DataItemBundleWidget(QWidget* parent)
     : QWidget(parent)
diff --git a/GUI/View/Common/DataItemBundleWidget.h b/GUI/View/Common/DataItemBundleWidget.h
index bbee50cb68d0b6bac94809fa7c2f7581f5a6ab7e..b3acafa0ed09d6844b0120b0c73906a16a735635 100644
--- a/GUI/View/Common/DataItemBundleWidget.h
+++ b/GUI/View/Common/DataItemBundleWidget.h
@@ -15,10 +15,11 @@
 #ifndef BORNAGAIN_GUI_VIEW_COMMON_DATAITEMBUNDLEWIDGET_H
 #define BORNAGAIN_GUI_VIEW_COMMON_DATAITEMBUNDLEWIDGET_H
 
-#include "GUI/Model/Data/IntensityDataItem.h"
-#include "GUI/Model/Data/SpecularDataItem.h"
 #include <QWidget>
 
+class IntensityDataItem;
+class SpecularDataItem;
+
 //! The DataItemBundleWidget class is a base for widgets, representing the SpecularDataItem and
 //! IntensityDataItem. It may store a list of SpecularDataItems that are required for
 //! simultaneous, synchronous work while plotting and changing their properties.
diff --git a/GUI/View/Mask/ColorMapSceneAdaptor.cpp b/GUI/View/Mask/ColorMapSceneAdaptor.cpp
index c2d16793fa399be534baafad5831065b37be032e..ddec1be5a63d91f360232a610e710a566a74f2ba 100644
--- a/GUI/View/Mask/ColorMapSceneAdaptor.cpp
+++ b/GUI/View/Mask/ColorMapSceneAdaptor.cpp
@@ -14,6 +14,7 @@
 
 #include "GUI/View/Mask/ColorMapSceneAdaptor.h"
 #include "GUI/View/PlotUtil/ColorMap.h"
+#include <QEvent>
 
 ColorMapSceneAdaptor::ColorMapSceneAdaptor()
     : m_plot(nullptr)
diff --git a/GUI/View/Plot2D/ColorMapCanvas.cpp b/GUI/View/Plot2D/ColorMapCanvas.cpp
index 7e8aa92c62104bdf0eee17e0c27415742e15e99b..8f1d08c184a55d52e55797a38445d279b0fd3965 100644
--- a/GUI/View/Plot2D/ColorMapCanvas.cpp
+++ b/GUI/View/Plot2D/ColorMapCanvas.cpp
@@ -17,6 +17,7 @@
 #include "GUI/View/PlotUtil/ColorMap.h"
 #include "GUI/View/PlotUtil/FontScalingEvent.h"
 #include "GUI/View/PlotUtil/PlotStatusLabel.h"
+#include <QVBoxLayout>
 
 ColorMapCanvas::ColorMapCanvas(QWidget* parent)
     : QWidget(parent)
diff --git a/GUI/View/Plot2D/IntensityDataCanvas.cpp b/GUI/View/Plot2D/IntensityDataCanvas.cpp
index b1b8473977e84cc6e4cf898edfe96c2eb13d65b8..07a317dc37e7e93a8889e1f677efab44c43a96fa 100644
--- a/GUI/View/Plot2D/IntensityDataCanvas.cpp
+++ b/GUI/View/Plot2D/IntensityDataCanvas.cpp
@@ -20,6 +20,8 @@
 #include "GUI/View/Plot2D/ColorMapCanvas.h"
 #include "GUI/View/PlotUtil/ColorMap.h"
 #include "GUI/View/PlotUtil/SavePlotAssistant.h"
+#include "qcustomplot.h"
+#include <QVBoxLayout>
 
 namespace {
 
diff --git a/GUI/View/PlotComparison/FitComparisonWidget.cpp b/GUI/View/PlotComparison/FitComparisonWidget.cpp
index 27c906dbb75b0bed06c5bb4d8f8b3fc852225405..e56b2160d44f767340b2d052e84cf63962933165 100644
--- a/GUI/View/PlotComparison/FitComparisonWidget.cpp
+++ b/GUI/View/PlotComparison/FitComparisonWidget.cpp
@@ -15,6 +15,7 @@
 #include "GUI/View/PlotComparison/FitComparisonWidget.h"
 #include "Device/Histo/DiffUtil.h"
 #include "GUI/Model/Data/IntensityDataItem.h"
+#include "GUI/Model/Data/SpecularDataItem.h"
 #include "GUI/Model/Job/FitSuiteItem.h"
 #include "GUI/Model/Project/ProjectDocument.h"
 #include "GUI/Util/ActionFactory.h"
@@ -25,6 +26,7 @@
 #include "GUI/View/PlotUtil/PlotStatusLabel.h"
 #include "GUI/View/PlotUtil/RangeUtils.h"
 #include <QAction>
+#include <QVBoxLayout>
 
 FitComparisonWidget::FitComparisonWidget(QWidget* parent)
     : DataAccessWidget(parent)
diff --git a/GUI/View/PlotSpecular/SpecularPlot.h b/GUI/View/PlotSpecular/SpecularPlot.h
index 443b60b4608bcaf8cc9841065ec9680f12274d1e..1c3be99b6b0c55608af6b9f672bb41bff841ea5f 100644
--- a/GUI/View/PlotSpecular/SpecularPlot.h
+++ b/GUI/View/PlotSpecular/SpecularPlot.h
@@ -19,6 +19,10 @@
 #include <memory>
 
 class BasicAxisItem;
+class QCPAxis;
+class QCPErrorBars;
+class QCPGraph;
+class QCPRange;
 class SpecularDataItem;
 class UpdateTimer;
 
diff --git a/GUI/View/PlotUtil/ColorMap.cpp b/GUI/View/PlotUtil/ColorMap.cpp
index b2228aa194ed3bdcac7e6e7ae695126676d730ac..9c1d0904bd9e1465c792c61fabd817d4b256de35 100644
--- a/GUI/View/PlotUtil/ColorMap.cpp
+++ b/GUI/View/PlotUtil/ColorMap.cpp
@@ -20,6 +20,7 @@
 #include "GUI/View/PlotUtil/PlotEventInfo.h"
 #include "GUI/View/PlotUtil/RangeUtils.h"
 #include "GUI/View/Tool/UpdateTimer.h"
+#include "qcustomplot.h"
 
 namespace {
 
diff --git a/GUI/View/PlotUtil/ColorMap.h b/GUI/View/PlotUtil/ColorMap.h
index 02953ba9cc654a0e6832480d2e5a347945712370..adedc8bc4998400b401e173d0d3d2ceb39174d04 100644
--- a/GUI/View/PlotUtil/ColorMap.h
+++ b/GUI/View/PlotUtil/ColorMap.h
@@ -18,6 +18,10 @@
 #include "GUI/View/PlotUtil/ScientificPlot.h"
 
 class IntensityDataItem;
+class QCPRange;
+class QCPColorScale;
+class QCPColorMap;
+class QCPLayoutGrid;
 class UpdateTimer;
 
 //! The ColorMap class presents 2D intensity data from IntensityDataItem as color map.
diff --git a/GUI/View/PlotUtil/SavePlotAssistant.cpp b/GUI/View/PlotUtil/SavePlotAssistant.cpp
index f6ff9ecc8fe4066e9ec7a3816a5cb46e1040ae52..5df2bbfb1662731de540a61e3fc9168fb99f5c47 100644
--- a/GUI/View/PlotUtil/SavePlotAssistant.cpp
+++ b/GUI/View/PlotUtil/SavePlotAssistant.cpp
@@ -17,6 +17,7 @@
 #include "Device/IO/IOFactory.h"
 #include "GUI/Application/ApplicationSettings.h"
 #include "GUI/View/PlotUtil/ColorMap.h"
+#include "qcustomplot.h"
 #include <QFileDialog>
 #include <QMessageBox>
 #include <QVector>
diff --git a/GUI/View/Projection/ProjectionsPlot.h b/GUI/View/Projection/ProjectionsPlot.h
index e1ea23ad3b22039d09e8a1f152c466e04f6e51b7..16fd81388bf779ba627692ec6d917e388f715361 100644
--- a/GUI/View/Projection/ProjectionsPlot.h
+++ b/GUI/View/Projection/ProjectionsPlot.h
@@ -23,7 +23,10 @@
 class Datafield;
 class IntensityDataItem;
 class MaskItem;
+class MaskItemObject;
 class ProjectionContainerItem;
+class QCPGraph;
+class QCustomPlot;
 
 //! A customplot based widget to display projections of IntensityDataItem on X,Y axes.