diff --git a/src/optimagic/parameters/conversion.py b/src/optimagic/parameters/conversion.py
index d087afcfd..602b545b7 100644
--- a/src/optimagic/parameters/conversion.py
+++ b/src/optimagic/parameters/conversion.py
@@ -5,6 +5,7 @@
 
 import numpy as np
 
+from optimagic.parameters.bounds import get_internal_bounds
 from optimagic.parameters.constraints import resolve_constraints, to_legacy_dicts
 from optimagic.parameters.scale_conversion import get_scale_converter
 from optimagic.parameters.space_conversion import InternalParams, get_space_converter
@@ -185,15 +186,7 @@ def _fast_derivative_to_internal(
         has_transforming_constraints=False,
     )
 
-    if bounds is None or bounds.lower is None:
-        lower_bounds = None
-    else:
-        lower_bounds = bounds.lower.astype(float)
-
-    if bounds is None or bounds.upper is None:
-        upper_bounds = None
-    else:
-        upper_bounds = bounds.upper.astype(float)
+    lower_bounds, upper_bounds = get_internal_bounds(params=params, bounds=bounds)
 
     internal_params = InternalParams(
         values=params.astype(float),
diff --git a/tests/optimagic/parameters/test_conversion.py b/tests/optimagic/parameters/test_conversion.py
index 68bc47828..dc8a6fd3c 100644
--- a/tests/optimagic/parameters/test_conversion.py
+++ b/tests/optimagic/parameters/test_conversion.py
@@ -13,7 +13,7 @@
 from optimagic.typing import AggregationLevel
 
 
-def test_get_converter_fast_case():
+def test_get_converter_fast_path():
     converter, internal = get_converter(
         params=np.arange(3),
         constraints=None,
@@ -35,6 +35,21 @@ def test_get_converter_fast_case():
     )
 
 
+@pytest.mark.parametrize("container", [list, tuple, np.array])
+def test_get_converter_fast_path_with_sequence_bounds(container):
+    converter, internal = get_converter(
+        params=np.arange(3),
+        constraints=None,
+        bounds=Bounds(lower=container([-1, -2, -3]), upper=container([1, 2, 3])),
+        func_eval=3,
+        derivative_eval=None,
+        solver_type=AggregationLevel.SCALAR,
+    )
+
+    aaae(internal.lower_bounds, np.array([-1, -2, -3]))
+    aaae(internal.upper_bounds, np.array([1, 2, 3]))
+
+
 def test_get_converter_with_constraints_and_bounds():
     bounds = Bounds(
         lower=np.array([-1, -np.inf, -np.inf]),