diff --git a/CGAL_ipelets/include/CGAL/CGAL_Ipelet_base.h b/CGAL_ipelets/include/CGAL/CGAL_Ipelet_base.h
index d7e2a670ea0..02d34fe6216 100644
--- a/CGAL_ipelets/include/CGAL/CGAL_Ipelet_base.h
+++ b/CGAL_ipelets/include/CGAL/CGAL_Ipelet_base.h
@@ -19,6 +19,8 @@
 // Author(s)     : Sebastien Loriot, Sylvain Pion
 
 
+#include <CGAL/config.h>
+
 #ifdef CGAL_USE_IPE_7
 #include <CGAL/CGAL_Ipelet_base_v7.h>
 #else
diff --git a/CGALimageIO/include/CGAL/Image_3_vtk_interface.h b/CGALimageIO/include/CGAL/Image_3_vtk_interface.h
index bb0587dacfb..ad74fdf9c43 100644
--- a/CGALimageIO/include/CGAL/Image_3_vtk_interface.h
+++ b/CGALimageIO/include/CGAL/Image_3_vtk_interface.h
@@ -17,9 +17,12 @@
 // 
 // Author(s)     : Laurent Rineau
 
+
 #ifndef CGAL_IMAGE_3_VTK_INTERFACE_H
 #define CGAL_IMAGE_3_VTK_INTERFACE_H
 
+#include <CGAL/config.h>
+
 #ifdef CGAL_USE_VTK
 #include <CGAL/Image_3.h>
 #include <vtkImageData.h>
diff --git a/Circular_kernel_2/include/CGAL/Circular_arc_2.h b/Circular_kernel_2/include/CGAL/Circular_arc_2.h
index fa28a24cfbc..4d72a741cd4 100644
--- a/Circular_kernel_2/include/CGAL/Circular_arc_2.h
+++ b/Circular_kernel_2/include/CGAL/Circular_arc_2.h
@@ -25,6 +25,8 @@
 #ifndef CGAL_CIRCULAR_ARC_2_H
 #define CGAL_CIRCULAR_ARC_2_H
 
+#include <CGAL/config.h>
+
 namespace CGAL {
   
 template <class CircularKernel> 
diff --git a/Kernel_23/include/CGAL/kernel_to_kernel.h b/Kernel_23/include/CGAL/kernel_to_kernel.h
index e3a6bcac3d1..2c04206324a 100644
--- a/Kernel_23/include/CGAL/kernel_to_kernel.h
+++ b/Kernel_23/include/CGAL/kernel_to_kernel.h
@@ -24,6 +24,8 @@
 #ifndef CGAL_KERNEL_TO_KERNEL_H
 #define CGAL_KERNEL_TO_KERNEL_H
 
+#include <CGAL/config.h>
+
 #ifdef CGAL_USE_LEDA
 #include <CGAL/LEDA_basic.h>
 #include <CGAL/leda_integer.h>
diff --git a/LEDA/include/CGAL/LEDA_basic.h b/LEDA/include/CGAL/LEDA_basic.h
index 7c1d99ad639..6ac4ad52207 100644
--- a/LEDA/include/CGAL/LEDA_basic.h
+++ b/LEDA/include/CGAL/LEDA_basic.h
@@ -21,9 +21,13 @@
 //
 // Author(s)     : Matthias Baesken
 
+
+
 #ifndef CGAL_LEDA_BASIC_H
 #define CGAL_LEDA_BASIC_H
 
+#include <CGAL/config.h>
+
 #ifdef CGAL_USE_LEDA
 // The following is needed for LEDA 4.4 due to min/max problems...
 #  define LEDA_NO_MIN_MAX_TEMPL
diff --git a/Nef_2/include/CGAL/Nef_2/geninfo.h b/Nef_2/include/CGAL/Nef_2/geninfo.h
index 232def6eb3f..d175ce1742f 100644
--- a/Nef_2/include/CGAL/Nef_2/geninfo.h
+++ b/Nef_2/include/CGAL/Nef_2/geninfo.h
@@ -20,6 +20,7 @@
 #ifndef CGAL_NEF_2_GENINFO_H
 #define CGAL_NEF_2_GENINFO_H
 
+#include <CGAL/config.h>
 #include <memory>
 
 /*{\Moptions outfile=geninfo.man}*/
diff --git a/Number_types/include/CGAL/mpfi_coercion_traits.h b/Number_types/include/CGAL/mpfi_coercion_traits.h
index bd811e6045d..3b8e657ca6b 100644
--- a/Number_types/include/CGAL/mpfi_coercion_traits.h
+++ b/Number_types/include/CGAL/mpfi_coercion_traits.h
@@ -16,9 +16,13 @@
 //
 // Author: Luis Peņaranda <luis.penaranda@loria.fr>
 
+
+
 #ifndef CGAL_MPFI_COERCION_TRAITS_H
 #define CGAL_MPFI_COERCION_TRAITS_H
 
+#include <CGAL/config.h>
+
 #ifdef CGAL_USE_MPFI
 
 #include <CGAL/number_type_basic.h>
diff --git a/Number_types/include/CGAL/mpfr_coercion_traits.h b/Number_types/include/CGAL/mpfr_coercion_traits.h
index 281f8b31084..15c7db8d459 100644
--- a/Number_types/include/CGAL/mpfr_coercion_traits.h
+++ b/Number_types/include/CGAL/mpfr_coercion_traits.h
@@ -19,6 +19,8 @@
 #ifndef CGAL_MPFR_COERCION_TRAITS_H
 #define CGAL_MPFR_COERCION_TRAITS_H
 
+#include <CGAL/config.h>
+
 #ifdef CGAL_USE_MPFR
 
 #include <CGAL/number_type_basic.h>
diff --git a/Number_types/include/CGAL/number_type_basic.h b/Number_types/include/CGAL/number_type_basic.h
index a8f53fa299f..1dd8d879e12 100644
--- a/Number_types/include/CGAL/number_type_basic.h
+++ b/Number_types/include/CGAL/number_type_basic.h
@@ -25,6 +25,8 @@
 #ifndef CGAL_NUMBER_TYPE_BASIC_H
 #define CGAL_NUMBER_TYPE_BASIC_H
 
+#include <CGAL/config.h>
+
 #define CGAL_PI 3.14159265358979323846
 
 
diff --git a/Polynomial/include/CGAL/Polynomial/polynomial_gcd.h b/Polynomial/include/CGAL/Polynomial/polynomial_gcd.h
index 516086c6db5..4f793b923a1 100644
--- a/Polynomial/include/CGAL/Polynomial/polynomial_gcd.h
+++ b/Polynomial/include/CGAL/Polynomial/polynomial_gcd.h
@@ -30,6 +30,8 @@
 #ifndef CGAL_POLYNOMIAL_GCD_H
 #define CGAL_POLYNOMIAL_GCD_H
 
+#include <CGAL/config.h>
+
 #ifndef CGAL_USE_INTERNAL_MODULAR_GCD
 #define CGAL_USE_INTERNAL_MODULAR_GCD 1
 #endif
diff --git a/Straight_skeleton_2/include/CGAL/Straight_skeleton_2/debug.h b/Straight_skeleton_2/include/CGAL/Straight_skeleton_2/debug.h
index 89a0c92b563..4784b106848 100644
--- a/Straight_skeleton_2/include/CGAL/Straight_skeleton_2/debug.h
+++ b/Straight_skeleton_2/include/CGAL/Straight_skeleton_2/debug.h
@@ -18,6 +18,8 @@
 #ifndef CGAL_STRAIGHT_SKELETON_DEBUG_H
 #define CGAL_STRAIGHT_SKELETON_DEBUG_H 1
 
+#include <CGAL/config.h>
+
 #ifdef CGAL_USE_CORE
 #  include <CGAL/CORE_BigFloat.h>
 #endif
diff --git a/Surface_mesher/include/CGAL/vtkSurfaceMesherContourFilter.h b/Surface_mesher/include/CGAL/vtkSurfaceMesherContourFilter.h
index 48785163787..0cc2f87a4c1 100644
--- a/Surface_mesher/include/CGAL/vtkSurfaceMesherContourFilter.h
+++ b/Surface_mesher/include/CGAL/vtkSurfaceMesherContourFilter.h
@@ -20,6 +20,9 @@
 #ifndef CGAL_VTK_SURFACE_MESHER_CONTOUR_FILTER_H
 #define CGAL_VTK_SURFACE_MESHER_CONTOUR_FILTER_H
 
+
+
+#include <CGAL/config.h>
 #include <vtkPolyDataAlgorithm.h>
 
 class vtkCGALSurfaceMesherContourFilter : public vtkPolyDataAlgorithm