diff --git a/GUI/Model/Project/ProjectDocument.h b/GUI/Model/Project/ProjectDocument.h
index 4491fa36b0fbcb594b1919d74221d30a095499ab..20684b85f63a6aaa7c08bc329918cec3f6d817b8 100644
--- a/GUI/Model/Project/ProjectDocument.h
+++ b/GUI/Model/Project/ProjectDocument.h
@@ -29,7 +29,6 @@ class MessageService;
 class OutputDataIOService;
 class InstrumentItems;
 class SampleModel;
-class MaterialModel;
 class RealDataModel;
 class JobModel;
 class LinkInstrumentManager;
diff --git a/GUI/View/FromDomain/GUIExamplesFactory.h b/GUI/View/FromDomain/GUIExamplesFactory.h
index c48cb0dce882e906c8af79ba91e40454c9d52854..ead7cffc55db37995f01bc0360cf6705875f187b 100644
--- a/GUI/View/FromDomain/GUIExamplesFactory.h
+++ b/GUI/View/FromDomain/GUIExamplesFactory.h
@@ -17,8 +17,6 @@
 
 #include <QString>
 
-class SampleModel;
-class MaterialModel;
 class MultiLayerItem;
 
 //! Class that generates GUI model from
diff --git a/GUI/View/FromDomain/GUIObjectBuilder.h b/GUI/View/FromDomain/GUIObjectBuilder.h
index 2cd66324feed5ecb26e14069a9e4ef2674004d9d..c256a13ac27b05d66456523a9e8fe9c9f11a077b 100644
--- a/GUI/View/FromDomain/GUIObjectBuilder.h
+++ b/GUI/View/FromDomain/GUIObjectBuilder.h
@@ -20,7 +20,6 @@
 class SimulationOptionsItem;
 class ISimulation;
 class InstrumentItems;
-class MaterialModel;
 class MultiLayer;
 class SampleModel;
 class SessionItem;
diff --git a/GUI/View/Project/PyImportAssistant.h b/GUI/View/Project/PyImportAssistant.h
index 46378ff9199d3ab1c3cc2380bcf3a1310f6b54d8..4a0ee3e76ce93e5e1432a1041e626dd336a2522a 100644
--- a/GUI/View/Project/PyImportAssistant.h
+++ b/GUI/View/Project/PyImportAssistant.h
@@ -20,7 +20,6 @@
 #include <memory>
 
 class SampleModel;
-class MaterialModel;
 class MultiLayerItem;
 class MultiLayer;