diff --git a/src/lcm/grids.py b/src/lcm/grids.py
index 9063eb5..9ea9843 100644
--- a/src/lcm/grids.py
+++ b/src/lcm/grids.py
@@ -198,9 +198,6 @@ def _validate_discrete_grid(category_class: type) -> None:
     if error_messages:
         msg = format_messages(error_messages)
         raise GridInitializationError(msg)
-    if error_messages:
-        msg = format_messages(error_messages)
-        raise GridInitializationError(msg)
 
 
 def _get_field_names_and_values(dc: type) -> dict[str, Any]:
diff --git a/tests/input_processing/test_discrete_state_conversion.py b/tests/input_processing/test_discrete_state_conversion.py
index d164e51..d0bb282 100644
--- a/tests/input_processing/test_discrete_state_conversion.py
+++ b/tests/input_processing/test_discrete_state_conversion.py
@@ -11,6 +11,7 @@
     _get_code_to_index_func,
     _get_discrete_vars_with_non_index_codes,
     _get_index_to_code_func,
+    _get_next_index_func,
     convert_arbitrary_codes_to_array_indices,
 )
 
@@ -147,3 +148,13 @@ def test_convert_discrete_codes_to_indices(model):
     assert got.states["__c_index__"].codes == (0, 1)
     assert got.functions["c"](0) == 1
     assert got.functions["c"](1) == 0
+
+
+def test_get_next_index_func():
+    got_func = _get_next_index_func(
+        next_func=lambda wealth, working: jnp.clip(wealth + working, 1, 3),
+        codes_array=jnp.array([1, 2, 3]),
+        name="wealth",
+    )
+    got = got_func(wealth=jnp.array([1, 2]), working=jnp.array([0, 1]))
+    assert_array_equal(got, jnp.array([0, 2]))