diff --git a/model/common/tests/interpolation_tests/test_interpolation_factory.py b/model/common/tests/interpolation_tests/test_interpolation_factory.py
index f2bb8b0f8..8f7f5e192 100644
--- a/model/common/tests/interpolation_tests/test_interpolation_factory.py
+++ b/model/common/tests/interpolation_tests/test_interpolation_factory.py
@@ -75,7 +75,7 @@ def get_interpolation_factory(
     backend, experiment, grid_file
 ) -> interpolation_factory.InterpolationFieldsFactory:
     registry_key = (
-        experiment.join(backend.name) if hasattr(backend, "name") else experiment.join("None")
+        experiment.join(backend.name) if hasattr(backend, "name") else experiment.join(str(backend))
     )
     factory = interpolation_factories.get(registry_key)
     if not factory:
diff --git a/model/testing/src/icon4py/model/testing/grid_utils.py b/model/testing/src/icon4py/model/testing/grid_utils.py
index ce5d44c16..0d828e1f8 100644
--- a/model/testing/src/icon4py/model/testing/grid_utils.py
+++ b/model/testing/src/icon4py/model/testing/grid_utils.py
@@ -135,7 +135,7 @@ def get_grid_geometry(
     xp = data_alloc.array_ns(on_gpu)
     num_levels = get_num_levels(experiment)
     register_name = (
-        experiment.join(backend.name) if hasattr(backend, "name") else experiment.join("None")
+        experiment.join(backend.name) if hasattr(backend, "name") else experiment.join(str(backend))
     )
 
     def construct_decomposition_info(grid: icon.IconGrid) -> definitions.DecompositionInfo: