diff --git a/src/lcm/input_processing/discrete_state_conversion.py b/src/lcm/input_processing/discrete_state_conversion.py
index 5d3216f..1ac6437 100644
--- a/src/lcm/input_processing/discrete_state_conversion.py
+++ b/src/lcm/input_processing/discrete_state_conversion.py
@@ -1,4 +1,3 @@
-import inspect
 from collections.abc import Callable
 from dataclasses import dataclass, field
 
@@ -100,8 +99,8 @@ def convert_discrete_options_to_indices(
 
         1. Remove the variable from the states or choices dictionary
         2. Replace it with a new state or choice with index options (__{var}_index__)
-        3. Add a function that maps the index options to the original options
-        4. Add updated next functions (if the variable was a state variable)
+        3. Add updated next functions (if the variable was a state variable)
+        4. Add a function that maps the index options to the original options
 
     Args:
         model: The model as provided by the user.
@@ -116,43 +115,34 @@ def convert_discrete_options_to_indices(
 
     non_index_discrete_vars = _get_discrete_vars_with_non_index_options(model)
 
+    # fast path
     if not non_index_discrete_vars:
-        # fast path
         return model, Converter()
 
     functions = model.functions.copy()
     states = model.states.copy()
     choices = model.choices.copy()
 
-    # Update next functions (needs to be done before updating the grids, otherwise the
-    # already updated state variables are being used)
-    # ----------------------------------------------------------------------------------
-    non_index_states = [s for s in states if s in non_index_discrete_vars]
-
-    for state in model.states:
-        next_func = model.functions[f"next_{state}"]
-        must_be_updated = _func_depends_on(next_func, depends_on=non_index_states)
-        if must_be_updated:
-            functions.pop(f"next_{state}")
-
-            functions[f"next___{state}_index__"] = _get_next_func_of_index_var(
-                next_func=next_func,
-                variables=non_index_states,
-            )
-
     # Update grids
     # ----------------------------------------------------------------------------------
     for var in non_index_discrete_vars:
         grid: DiscreteGrid = gridspecs[var]  # type: ignore[assignment]
         index_grid = DiscreteGrid(options=list(range(len(grid.options))))
 
-        if var in states:
+        if var in model.states:
             states.pop(var)
             states[f"__{var}_index__"] = index_grid
         else:
             choices.pop(var)
             choices[f"__{var}_index__"] = index_grid
 
+    # Update next functions
+    # ----------------------------------------------------------------------------------
+    non_index_states = [s for s in model.states if s in non_index_discrete_vars]
+
+    for var in non_index_states:
+        functions[f"next___{var}_index__"] = functions.pop(f"next_{var}")
+
     # Add index to label functions
     # ----------------------------------------------------------------------------------
     index_to_label_funcs = {
@@ -189,28 +179,6 @@ def convert_discrete_options_to_indices(
     return new_model, converter
 
 
-def _get_next_func_of_index_var(next_func: Callable, variables: list[str]) -> Callable:
-    """Create next function for corresponding index variable."""
-    arg_names = list(inspect.signature(next_func).parameters)
-
-    relevant_vars = [var for var in variables if var in arg_names]
-
-    if not relevant_vars:
-        return next_func
-
-    for var in relevant_vars:
-        arg_names[arg_names.index(var)] = f"__{var}_index__"
-
-    @with_signature(args=arg_names)
-    def next_func_of_index_var(*args, **kwargs):
-        kwargs = all_as_kwargs(args, kwargs, arg_names=arg_names)
-        for var in relevant_vars:
-            kwargs[var] = kwargs.pop(f"__{var}_index__")
-        return next_func(**kwargs)
-
-    return next_func_of_index_var
-
-
 def _get_discrete_vars_with_non_index_options(model: Model) -> list[str]:
     """Get discrete variables with non-index options.
 
@@ -274,9 +242,3 @@ def label_to_index(*args, **kwargs):
         return jnp.argmax(data[:, None] == labels_array[None, :], axis=1)
 
     return label_to_index
-
-
-def _func_depends_on(func: Callable, depends_on: list[str]) -> bool:
-    """Check if any function argument is in the list depends_on."""
-    arg_names = list(inspect.signature(func).parameters)
-    return any(arg in depends_on for arg in arg_names)
diff --git a/tests/input_processing/test_discrete_state_conversion.py b/tests/input_processing/test_discrete_state_conversion.py
index 92de16b..f34efe2 100644
--- a/tests/input_processing/test_discrete_state_conversion.py
+++ b/tests/input_processing/test_discrete_state_conversion.py
@@ -7,10 +7,8 @@
 
 from lcm import DiscreteGrid
 from lcm.input_processing.discrete_state_conversion import (
-    _func_depends_on,
     _get_discrete_vars_with_non_index_options,
     _get_index_to_label_func,
-    _get_next_func_of_index_var,
     convert_discrete_options_to_indices,
 )
 
@@ -73,20 +71,3 @@ def test_convert_discrete_options_to_indices(model):
     assert_array_equal(got.states["__c_index__"], DiscreteGrid([0, 1]))
     assert got.functions["c"](0) == 1
     assert got.functions["c"](1) == 10
-
-
-def test_func_depends_on():
-    def foo(a, b):
-        pass
-
-    assert _func_depends_on(foo, depends_on=["a", "b"])
-    assert not _func_depends_on(foo, depends_on=["c"])
-
-
-def test_get_next_func_of_index_var():
-    def next_a(a):
-        return a
-
-    got = _get_next_func_of_index_var(next_a, variables=["a"])
-    assert got(__a_index__=0) == 0
-    assert got(2) == 2