diff --git a/GUI/Model/Sample/ParticleItem.cpp b/GUI/Model/Sample/ParticleItem.cpp
index 7a34bbecd9c4181db98628533777127e333fc56b..d619b2ca79cd97beea6ba78952d4c021433e4619 100644
--- a/GUI/Model/Sample/ParticleItem.cpp
+++ b/GUI/Model/Sample/ParticleItem.cpp
@@ -19,6 +19,7 @@
 #include "GUI/Model/Sample/MaterialItem.h"
 #include "GUI/Model/Sample/ParticleCoreShellItem.h"
 #include "GUI/Support/XML/Serialize.h"
+#include "Sample/Particle/IFormFactor.h"
 #include "Sample/Particle/Particle.h"
 #include "Sample/Scattering/Rotations.h"
 
diff --git a/GUI/View/Realspace/RealSpaceBuilderUtils.cpp b/GUI/View/Realspace/RealSpaceBuilderUtils.cpp
index b04f611e596a81c80d0a2bcef416fb48dfa9fed7..b2182695e2cc3c61d4367d78acc09a00bb6f1ed8 100644
--- a/GUI/View/Realspace/RealSpaceBuilderUtils.cpp
+++ b/GUI/View/Realspace/RealSpaceBuilderUtils.cpp
@@ -27,6 +27,7 @@
 #include "GUI/View/Realspace/RealSpaceMesoCrystalUtils.h"
 #include "GUI/View/Realspace/TransformTo3D.h"
 #include "Resample/Particle/ReParticle.h"
+#include "Sample/Particle/IFormFactor.h"
 #include "Sample/Particle/MesoCrystal.h"
 #include "Sample/Particle/Particle.h"
 #include "Sample/Particle/ParticleCoreShell.h"
diff --git a/Sample/Particle/Particle.cpp b/Sample/Particle/Particle.cpp
index df65d46d7538ba44cd20f3b4d052ec6f6ad999de..1e752abe5d6a87b90c5f718b09d0b4fdcd790e09 100644
--- a/Sample/Particle/Particle.cpp
+++ b/Sample/Particle/Particle.cpp
@@ -15,6 +15,7 @@
 #include "Sample/Particle/Particle.h"
 #include "Base/Util/Assert.h"
 #include "Base/Vector/RotMatrix.h"
+#include "Sample/Particle/IFormFactor.h"
 #include "Sample/Scattering/Rotations.h"
 
 Particle::Particle(Material material, const IFormFactor& formfactor)
diff --git a/Sample/Particle/Particle.h b/Sample/Particle/Particle.h
index fa0d6e0606498edc78a86161cb7d7323da2e6b46..cc71743842560d44f5d96a2f28cbbe2ac6fa4e62 100644
--- a/Sample/Particle/Particle.h
+++ b/Sample/Particle/Particle.h
@@ -16,9 +16,10 @@
 #define BORNAGAIN_SAMPLE_PARTICLE_PARTICLE_H
 
 #include "Sample/Material/Material.h"
-#include "Sample/Particle/IFormFactor.h"
 #include "Sample/Particle/IParticle.h"
 
+class IFormFactor;
+
 //! A particle with a form factor and refractive index.
 //! @ingroup samples
 
diff --git a/Sim/Export/SampleToPython.cpp b/Sim/Export/SampleToPython.cpp
index 410fdc359fbb8b2694bb8130c37622166eb2f4d0..3d9a46567d720514c406f898e29e61f32fc65a01 100644
--- a/Sim/Export/SampleToPython.cpp
+++ b/Sim/Export/SampleToPython.cpp
@@ -24,6 +24,7 @@
 #include "Sample/Multilayer/Layer.h"
 #include "Sample/Multilayer/MultiLayer.h"
 #include "Sample/Particle/Crystal.h"
+#include "Sample/Particle/IFormFactor.h"
 #include "Sample/Particle/MesoCrystal.h"
 #include "Sample/Particle/Particle.h"
 #include "Sample/Particle/ParticleComposition.h"
diff --git a/auto/Wrap/doxygenSample.i b/auto/Wrap/doxygenSample.i
index 5721b26fba99e7a6fbc0255dd7f7b5b01125343a..0ee325ad6cc467008d8441e6f58ad4f703fec546 100644
--- a/auto/Wrap/doxygenSample.i
+++ b/auto/Wrap/doxygenSample.i
@@ -5616,8 +5616,6 @@ magnetization (in A/m)
 
 
 // File: Particle_8cpp.xml
-%feature("docstring")  validate "std::string validate() const
-";
 
 
 // File: Particle_8h.xml