diff --git a/ogre/src/OgreMeshFactory.cc b/ogre/src/OgreMeshFactory.cc
index d30c55a79..431e3c832 100644
--- a/ogre/src/OgreMeshFactory.cc
+++ b/ogre/src/OgreMeshFactory.cc
@@ -409,7 +409,10 @@ bool OgreMeshFactory::LoadImpl(const MeshDescriptor &_desc)
         *indices++ = subMesh.Index(j);
 
       common::MaterialPtr material;
-      material = _desc.mesh->MaterialByIndex(subMesh.MaterialIndex());
+      if (const auto subMeshIdx = subMesh.GetMaterialIndex())
+      {
+        material = _desc.mesh->MaterialByIndex(subMeshIdx.value());
+      }
 
       MaterialPtr mat = this->scene->CreateMaterial();
       if (material)
diff --git a/ogre2/src/Ogre2MeshFactory.cc b/ogre2/src/Ogre2MeshFactory.cc
index 82d392abb..807f24d98 100644
--- a/ogre2/src/Ogre2MeshFactory.cc
+++ b/ogre2/src/Ogre2MeshFactory.cc
@@ -469,7 +469,10 @@ bool Ogre2MeshFactory::LoadImpl(const MeshDescriptor &_desc)
       iBuf->unlock();
 
       common::MaterialPtr material;
-      material = _desc.mesh->MaterialByIndex(subMesh.MaterialIndex());
+      if (const auto subMeshIdx = subMesh.GetMaterialIndex())
+      {
+        material = _desc.mesh->MaterialByIndex(subMeshIdx.value());
+      }
 
       MaterialPtr mat = this->scene->CreateMaterial();
       if (material)
diff --git a/optix/src/OptixMeshFactory.cc b/optix/src/OptixMeshFactory.cc
index 8788a3f2c..24ad23035 100644
--- a/optix/src/OptixMeshFactory.cc
+++ b/optix/src/OptixMeshFactory.cc
@@ -125,7 +125,10 @@ OptixSubMeshStorePtr OptixSubMeshStoreFactory::Create(
       sm->optixGeomInstance->setGeometry(optixGeometry);
 
       common::MaterialPtr material;
-      material = _desc.mesh->MaterialByIndex(subMesh->MaterialIndex());
+      if (const auto subMeshIdx = SubMesh.GetMaterialIndex())
+      {
+        material = _desc.mesh->MaterialByIndex(subMeshIdx.value());
+      }
       MaterialPtr mat = this->scene->CreateMaterial();
       if (material)
       {