diff --git a/GUI/Model/Project/ProjectDocument.cpp b/GUI/Model/Project/ProjectDocument.cpp
index 577d97125a025b1471fe80378cf3a05c220e92d3..7c0f520f3449df2e0c933e2730c8f97f29dcb617 100644
--- a/GUI/Model/Project/ProjectDocument.cpp
+++ b/GUI/Model/Project/ProjectDocument.cpp
@@ -122,9 +122,9 @@ InstrumentModel* ProjectDocument::instrumentModel() const
     return const_cast<InstrumentModel*>(&m_instrumentModel);
 }
 
-SampleModel* ProjectDocument::sampleModel()
+SampleModel* ProjectDocument::sampleModel() const
 {
-    return &m_sampleModel;
+    return const_cast<SampleModel*>(&m_sampleModel);
 }
 
 RealModel* ProjectDocument::realModel() const
diff --git a/GUI/Model/Project/ProjectDocument.h b/GUI/Model/Project/ProjectDocument.h
index 9878c1a2add3366ef0562d4deadc37049b12d56a..1f48b3e2892155e5f818b04b96259f3cef04ddc3 100644
--- a/GUI/Model/Project/ProjectDocument.h
+++ b/GUI/Model/Project/ProjectDocument.h
@@ -73,7 +73,7 @@ public:
     void setProjectFullPath(const QString& fullPath);
 
     InstrumentModel* instrumentModel() const;
-    SampleModel* sampleModel();
+    SampleModel* sampleModel() const;
     RealModel* realModel() const;
     JobModel* jobModel() const;
     SimulationOptionsItem* simulationOptionsItem();