diff --git a/Tests/NumLib/TestShapeFunctions.cpp b/Tests/NumLib/TestShapeFunctions.cpp
index ccf59c83fcdb15f8f46d1bba716927ab9cc480d0..3ca04502a6d28368ee96a5286418ce6fa9bfdde6 100644
--- a/Tests/NumLib/TestShapeFunctions.cpp
+++ b/Tests/NumLib/TestShapeFunctions.cpp
@@ -74,6 +74,7 @@ struct NaturalPointGenerator
                                [](double const& v) { return 1. - v; });
             return mapped_tuple;
         }
+        OGS_FATAL("NaturalPointGenerator: Unknown shape function type.");
     }
 
     result_type operator()(std::size_t /*size*/ = 0)