diff --git a/ereg/functional.py b/ereg/functional.py
index 4bed1f9..9e432a5 100644
--- a/ereg/functional.py
+++ b/ereg/functional.py
@@ -10,7 +10,7 @@ def registration_function(
     target_image: Union[str, sitk.Image],
     moving_image: Union[str, sitk.Image],
     output_image: str,
-    configuration: str = None,
+    configuration: Union[str, dict] = None,
     transform_file: str = None,
     log_file: str = None,
     **kwargs,
@@ -22,7 +22,7 @@ def registration_function(
         target_image (Union[str, sitk.Image]): The target image.
         moving_image (Union[str, sitk.Image]): The moving image.
         output_image (str): The output image.
-        config_file (str, optional): The config file for the registration. Defaults to None.
+        configuration (Union[str, dict], optional): The configuration file or dictionary. Defaults to None.
         transform_file (str, optional): The transform file. Defaults to None.
 
     Returns:
diff --git a/ereg/registration.py b/ereg/registration.py
index d3e0dea..5c27ba1 100644
--- a/ereg/registration.py
+++ b/ereg/registration.py
@@ -150,7 +150,7 @@ def register(
         target_image = read_image_and_cast_to_32bit_float(target_image)
         moving_image = read_image_and_cast_to_32bit_float(moving_image)
 
-        if self.parameters["bias_correct"]:
+        if self.parameters.get("bias"):
             self.logger.info("Bias correcting images.")
             target_image = self._bias_correct_image(target_image)
             moving_image = self._bias_correct_image(moving_image)
diff --git a/unit_tests/test_full.py b/unit_tests/test_full.py
index a71355b..536c70d 100644
--- a/unit_tests/test_full.py
+++ b/unit_tests/test_full.py
@@ -89,7 +89,7 @@ def test_registration_function():
         tempfile.gettempdir(), "tcia_aaac_t1ce_registered.nii.gz"
     )
     atlas_sri = os.path.join(atlas_data_dir, "sri24", "image.nii.gz")
-    test_config = {"initialization": "moments"}
+    test_config = {"initialization": "moments", "bias": True}
     registration_function(
         target_image=atlas_sri,
         moving_image=moving_image,