diff --git a/libsrc/occ/occgenmesh.cpp b/libsrc/occ/occgenmesh.cpp
index 656b8e36..7eb2d77d 100644
--- a/libsrc/occ/occgenmesh.cpp
+++ b/libsrc/occ/occgenmesh.cpp
@@ -669,6 +669,8 @@ namespace netgen
                 BRepMesh_IncrementalMesh (geom.shape, 0.01, true);
                 triangulation = BRep_Tool::Triangulation (face, loc);
               }
+            if(triangulation.IsNull())
+              throw Exception("OCC-Triangulation could not be built. Do you have a bounded shape?");
 
             BRepAdaptor_Surface sf(face, Standard_True);
             // one prop for evaluating and one for derivatives