diff --git a/src/App/DocumentObjectExtension.cpp b/src/App/DocumentObjectExtension.cpp
index adf670baf9..fbfd650d9a 100644
--- a/src/App/DocumentObjectExtension.cpp
+++ b/src/App/DocumentObjectExtension.cpp
@@ -25,6 +25,8 @@
 
 #include "DocumentObjectExtension.h"
 #include "DocumentObjectExtensionPy.h"
+#include "DocumentObject.h"
+#include "ExtensionContainer.h"
 
 using namespace App;
 
diff --git a/src/App/DocumentObjectExtension.h b/src/App/DocumentObjectExtension.h
index 9ec695ad7a..9bcdeebff7 100644
--- a/src/App/DocumentObjectExtension.h
+++ b/src/App/DocumentObjectExtension.h
@@ -24,9 +24,12 @@
 #ifndef APP_DOCUMENTOBJECTEXTENSION_H
 #define APP_DOCUMENTOBJECTEXTENSION_H
 
-#include "DocumentObject.h"
+#include "Extension.h"
+#include <Base/Matrix.h>
 
 namespace App {
+class DocumentObject;
+class DocumentObjectExecReturn;
 
 /**
  * @brief Extension with special document object calls
diff --git a/src/App/DocumentObserverPython.cpp b/src/App/DocumentObserverPython.cpp
index 71b113084c..3cf6bbaf3a 100644
--- a/src/App/DocumentObserverPython.cpp
+++ b/src/App/DocumentObserverPython.cpp
@@ -27,6 +27,7 @@
 #include "Document.h"
 #include "DocumentObject.h"
 #include "DocumentObserverPython.h"
+#include <Base/Interpreter.h>
 
 
 using namespace App;
diff --git a/src/App/DocumentPyImp.cpp b/src/App/DocumentPyImp.cpp
index e00367cbd8..4f7bc1a6f9 100644
--- a/src/App/DocumentPyImp.cpp
+++ b/src/App/DocumentPyImp.cpp
@@ -24,6 +24,7 @@
 #include "PreCompiled.h"
 
 #include <Base/FileInfo.h>
+#include <Base/Interpreter.h>
 
 #include "Document.h"
 #include "DocumentObject.h"
diff --git a/src/App/Enumeration.cpp b/src/App/Enumeration.cpp
index 8baf7f6775..4855bc34a8 100644
--- a/src/App/Enumeration.cpp
+++ b/src/App/Enumeration.cpp
@@ -24,7 +24,6 @@
 #ifndef _PreComp_
 # include <cassert>
 # include <cstring>
-# include <cstdlib>
 #endif
 
 #include <Base/Exception.h>
diff --git a/src/App/Enumeration.h b/src/App/Enumeration.h
index 27c545e43c..99747c8ea6 100644
--- a/src/App/Enumeration.h
+++ b/src/App/Enumeration.h
@@ -27,7 +27,6 @@
 #include <string>
 #include <vector>
 
-//#include <App/PropertyStandard.h>
 
 namespace App
 {
diff --git a/src/App/Expression.cpp b/src/App/Expression.cpp
index eeec710de3..37e27aaf55 100644
--- a/src/App/Expression.cpp
+++ b/src/App/Expression.cpp
@@ -31,36 +31,27 @@
 #endif
 
 #include <boost/algorithm/string/predicate.hpp>
-#include <boost/io/ios_state.hpp>
-
-#include <Base/Console.h>
-#include "Base/Exception.h"
-#include <Base/Interpreter.h>
-#include <App/Application.h>
-#include <App/Document.h>
-#include <App/DocumentPy.h>
-#include <App/DocumentObject.h>
-#include <App/PropertyUnits.h>
-#include <Base/QuantityPy.h>
-#include <Base/MatrixPy.h>
-#include <Base/PlacementPy.h>
-#include <Base/RotationPy.h>
-#include <Base/VectorPy.h>
-#include <QStringList>
-#include <string>
-#include <sstream>
-#include <math.h>
-#include <stdio.h>
-#include <stack>
-#include <deque>
-#include <algorithm>
-#include "ExpressionParser.h"
-#include <Base/Unit.h>
-#include <App/PropertyUnits.h>
-#include <App/ObjectIdentifier.h>
 #include <boost/math/special_functions/round.hpp>
 #include <boost/math/special_functions/trunc.hpp>
 
+#include <sstream>
+#include <stack>
+#include <string>
+
+#include <App/Application.h>
+#include <App/DocumentObject.h>
+#include <App/ObjectIdentifier.h>
+#include <App/PropertyUnits.h>
+#include <Base/Interpreter.h>
+#include <Base/MatrixPy.h>
+#include <Base/PlacementPy.h>
+#include <Base/QuantityPy.h>
+#include <Base/RotationPy.h>
+#include <Base/VectorPy.h>
+
+#include "ExpressionParser.h"
+
+
 /** \defgroup Expression Expressions framework
     \ingroup APP
     \brief The expression system allows users to write expressions and formulas that produce values
@@ -69,7 +60,7 @@
 using namespace Base;
 using namespace App;
 
-FC_LOG_LEVEL_INIT("Expression",true,true)
+FC_LOG_LEVEL_INIT("Expression", true, true)
 
 #ifndef M_PI
 #define M_PI       3.14159265358979323846
diff --git a/src/App/Expression.h b/src/App/Expression.h
index 926e72c99c..2c6034c37c 100644
--- a/src/App/Expression.h
+++ b/src/App/Expression.h
@@ -23,17 +23,17 @@
 #ifndef EXPRESSION_H
 #define EXPRESSION_H
 
+#include <deque>
+#include <set>
 #include <string>
-#include <tuple>
-#include <Base/Exception.h>
-#include <Base/Unit.h>
+
 #include <App/PropertyLinks.h>
 #include <App/ObjectIdentifier.h>
+#include <App/Range.h>
+#include <Base/Exception.h>
 #include <Base/BaseClass.h>
 #include <Base/Quantity.h>
-#include <set>
-#include <deque>
-#include <App/Range.h>
+
 
 #if defined(__clang__)
 # pragma clang diagnostic push
diff --git a/src/App/ExpressionParser.h b/src/App/ExpressionParser.h
index a10c1e8212..7ba3d3ca28 100644
--- a/src/App/ExpressionParser.h
+++ b/src/App/ExpressionParser.h
@@ -25,7 +25,6 @@
 #ifndef EXPRESSION_PARSER_H
 #define EXPRESSION_PARSER_H
 
-#include <Base/Interpreter.h>
 #include "Expression.h"
 
 namespace App {
diff --git a/src/App/ExpressionVisitors.h b/src/App/ExpressionVisitors.h
index 847c1265c3..6b9949ef92 100644
--- a/src/App/ExpressionVisitors.h
+++ b/src/App/ExpressionVisitors.h
@@ -23,7 +23,6 @@
 #ifndef RENAMEOBJECTIDENTIFIEREXPRESSIONVISITOR_H
 #define RENAMEOBJECTIDENTIFIEREXPRESSIONVISITOR_H
 
-#include <Base/BaseClass.h>
 #include "Expression.h"
 
 namespace App {
diff --git a/src/App/Extension.cpp b/src/App/Extension.cpp
index 18e21d5f1e..3f5c623c99 100644
--- a/src/App/Extension.cpp
+++ b/src/App/Extension.cpp
@@ -25,16 +25,15 @@
 
 #ifndef _PreComp_
 # include <cassert>
-# include <algorithm>
 #endif
 
-#include "Extension.h"
-#include "DocumentObject.h"
-#include "Base/Exception.h"
-#include <Base/Console.h>
 #include <Base/PyObjectBase.h>
+
+#include "Extension.h"
+#include "ExtensionContainer.h"
 #include <ExtensionPy.h>
 
+
 /* We do not use a standard property macro for type initiation. The reason is that we have the first
  * PropertyData in the extension chain, there is no parent property data.
  */
diff --git a/src/App/Extension.h b/src/App/Extension.h
index 4f2da76a06..b4c54a8874 100644
--- a/src/App/Extension.h
+++ b/src/App/Extension.h
@@ -24,11 +24,11 @@
 #ifndef APP_EXTENSION_H
 #define APP_EXTENSION_H
 
+#include <Base/Interpreter.h>
+
 #include "PropertyContainer.h"
 #include "PropertyPythonObject.h"
-#include "ExtensionContainer.h"
-#include "Base/Interpreter.h"
-#include <CXX/Objects.hxx>
+
 
 namespace App {
 
diff --git a/src/App/ExtensionContainer.cpp b/src/App/ExtensionContainer.cpp
index 528cd5ee4a..6c0014c997 100644
--- a/src/App/ExtensionContainer.cpp
+++ b/src/App/ExtensionContainer.cpp
@@ -23,15 +23,12 @@
 
 #include "PreCompiled.h"
 
-#ifndef _PreComp_
-# include <cassert>
-# include <algorithm>
-#endif
+#include <Base/Console.h>
+#include <Base/Exception.h>
 
 #include "Extension.h"
-#include "DocumentObject.h"
-#include "Base/Exception.h"
-#include <Base/Console.h>
+#include "ExtensionContainer.h"
+
 
 using namespace App;
 
diff --git a/src/App/ExtensionContainer.h b/src/App/ExtensionContainer.h
index ec44365462..1c36d98c01 100644
--- a/src/App/ExtensionContainer.h
+++ b/src/App/ExtensionContainer.h
@@ -24,16 +24,15 @@
 #ifndef APP_EXTENSIONCONTAINER_H
 #define APP_EXTENSIONCONTAINER_H
 
-#include "Extension.h"
-#include "PropertyContainer.h"
-#include "PropertyPythonObject.h"
-#include "DynamicProperty.h"
-#include <CXX/Objects.hxx>
-#include <Base/Writer.h>
 #include <Base/Reader.h>
+#include <Base/Writer.h>
+
+#include "PropertyContainer.h"
+
 
 namespace App {
 
+class Extension;
 /**
  * @brief Container which can hold extensions
  *
diff --git a/src/App/ExtensionContainerPyImp.cpp b/src/App/ExtensionContainerPyImp.cpp
index a7f6705887..1b965e0803 100644
--- a/src/App/ExtensionContainerPyImp.cpp
+++ b/src/App/ExtensionContainerPyImp.cpp
@@ -28,11 +28,10 @@
 #endif
 
 #include "Application.h"
-#include "DocumentObject.h"
 
-// inclution of the generated files (generated out of PropertyContainerPy.xml)
 #include <App/ExtensionContainerPy.h>
 #include <App/ExtensionContainerPy.cpp>
+#include <App/Extension.h>
 
 using namespace App;
 
diff --git a/src/App/ExtensionPyImp.cpp b/src/App/ExtensionPyImp.cpp
index ce1c2b9e9c..5ce2d58c8f 100644
--- a/src/App/ExtensionPyImp.cpp
+++ b/src/App/ExtensionPyImp.cpp
@@ -23,10 +23,6 @@
 
 #include "PreCompiled.h"
 
-#ifndef _PreComp_
-# include <sstream>
-#endif
-
 #include "Application.h"
 
 // inclution of the generated files (generated out of PropertyContainerPy.xml)
diff --git a/src/App/PropertyPythonObject.cpp b/src/App/PropertyPythonObject.cpp
index b8433162f5..895faf7b7f 100644
--- a/src/App/PropertyPythonObject.cpp
+++ b/src/App/PropertyPythonObject.cpp
@@ -28,6 +28,7 @@
 
 #include <Base/Base64.h>
 #include <Base/Console.h>
+#include <Base/Interpreter.h>
 #include <Base/Reader.h>
 #include <Base/Writer.h>
 
diff --git a/src/App/PropertyStandard.cpp b/src/App/PropertyStandard.cpp
index 2847560f5f..cf84b57421 100644
--- a/src/App/PropertyStandard.cpp
+++ b/src/App/PropertyStandard.cpp
@@ -28,6 +28,7 @@
 
 #include <Base/Console.h>
 #include <Base/Exception.h>
+#include <Base/Interpreter.h>
 #include <Base/Reader.h>
 #include <Base/Writer.h>
 #include <Base/Quantity.h>
diff --git a/src/Gui/Action.cpp b/src/Gui/Action.cpp
index 8ed2cbaa8e..a30b67fa91 100644
--- a/src/Gui/Action.cpp
+++ b/src/Gui/Action.cpp
@@ -36,6 +36,7 @@
 #endif
 
 #include <Base/Exception.h>
+#include <Base/Interpreter.h>
 #include <Base/Tools.h>
 
 #include "Action.h"
diff --git a/src/Gui/AxisOriginPyImp.cpp b/src/Gui/AxisOriginPyImp.cpp
index 824cee7e57..a84d105197 100644
--- a/src/Gui/AxisOriginPyImp.cpp
+++ b/src/Gui/AxisOriginPyImp.cpp
@@ -29,6 +29,7 @@
 
 #include "AxisOriginPy.h"
 #include "AxisOriginPy.cpp"
+#include <Base/Interpreter.h>
 
 using namespace Gui;
 
diff --git a/src/Gui/DlgPropertyLink.cpp b/src/Gui/DlgPropertyLink.cpp
index 7b7af21c2d..5d8cd40cd6 100644
--- a/src/Gui/DlgPropertyLink.cpp
+++ b/src/Gui/DlgPropertyLink.cpp
@@ -32,12 +32,14 @@
 
 #include <QStyledItemDelegate>
 
+#include <Base/Interpreter.h>
 #include <Base/Tools.h>
 #include <App/Application.h>
 #include <App/Document.h>
 #include <App/DocumentObject.h>
 #include <App/GeoFeature.h>
 #include <App/DocumentObserver.h>
+#include <App/PropertyPythonObject.h>
 
 #include "Document.h"
 #include "View3DInventor.h"
diff --git a/src/Gui/MDIView.cpp b/src/Gui/MDIView.cpp
index 5de18f7b63..1966016a48 100644
--- a/src/Gui/MDIView.cpp
+++ b/src/Gui/MDIView.cpp
@@ -45,6 +45,7 @@
 #include "Application.h"
 #include "MainWindow.h"
 #include "ViewProviderDocumentObject.h"
+#include <Base/Interpreter.h>
 
 using namespace Gui;
 namespace bp = boost::placeholders;
diff --git a/src/Gui/Selection.cpp b/src/Gui/Selection.cpp
index 385d356cba..7d48a5958e 100644
--- a/src/Gui/Selection.cpp
+++ b/src/Gui/Selection.cpp
@@ -36,6 +36,7 @@
 #include <App/GeoFeature.h>
 #include <Base/Console.h>
 #include <Base/Exception.h>
+#include <Base/Interpreter.h>
 #include <Base/Tools.h>
 #include <Base/UnitsApi.h>
 
diff --git a/src/Gui/View3DInventor.cpp b/src/Gui/View3DInventor.cpp
index 47cb6bc16e..1acb2b488b 100644
--- a/src/Gui/View3DInventor.cpp
+++ b/src/Gui/View3DInventor.cpp
@@ -63,6 +63,7 @@
 #include <Base/Exception.h>
 #include <Base/Console.h>
 #include <Base/FileInfo.h>
+#include <Base/Interpreter.h>
 
 #include <App/DocumentObject.h>
 
diff --git a/src/Mod/Mesh/App/Exporter.cpp b/src/Mod/Mesh/App/Exporter.cpp
index 5be6ba4ae5..3664d5705c 100644
--- a/src/Mod/Mesh/App/Exporter.cpp
+++ b/src/Mod/Mesh/App/Exporter.cpp
@@ -35,6 +35,7 @@
 #include "Base/Console.h"
 #include "Base/Exception.h"
 #include "Base/FileInfo.h"
+#include <Base/Interpreter.h>
 #include "Base/Sequencer.h"
 #include "Base/Stream.h"
 #include "Base/Tools.h"
diff --git a/src/Mod/Part/Gui/TaskDimension.cpp b/src/Mod/Part/Gui/TaskDimension.cpp
index 328120e039..c9fac9bc05 100644
--- a/src/Mod/Part/Gui/TaskDimension.cpp
+++ b/src/Mod/Part/Gui/TaskDimension.cpp
@@ -67,6 +67,7 @@
 #endif
 
 #include <Base/Console.h>
+#include <Base/Interpreter.h>
 #include <Base/UnitsApi.h>
 #include "../App/PartFeature.h"
 #include <Gui/Application.h>
diff --git a/src/Mod/Spreadsheet/App/PropertySheet.cpp b/src/Mod/Spreadsheet/App/PropertySheet.cpp
index 949d947451..3b13d77c6b 100644
--- a/src/Mod/Spreadsheet/App/PropertySheet.cpp
+++ b/src/Mod/Spreadsheet/App/PropertySheet.cpp
@@ -34,6 +34,7 @@
 #include <App/Document.h>
 #include <App/DocumentObject.h>
 #include <App/Property.h>
+#include <Base/Interpreter.h>
 #include <Base/Writer.h>
 #include <Base/Reader.h>
 #include <Base/Tools.h>
diff --git a/src/Mod/Spreadsheet/Gui/SheetModel.cpp b/src/Mod/Spreadsheet/Gui/SheetModel.cpp
index 7047f004e7..8841812592 100644
--- a/src/Mod/Spreadsheet/Gui/SheetModel.cpp
+++ b/src/Mod/Spreadsheet/Gui/SheetModel.cpp
@@ -36,6 +36,7 @@
 #include <Mod/Spreadsheet/App/Utils.h>
 #include "../App/Sheet.h"
 #include <Gui/Command.h>
+#include <Base/Interpreter.h>
 #include <Base/Tools.h>
 #include <Base/UnitsApi.h>
 #include <boost_bind_bind.hpp>