diff --git a/cdisc_rules_engine/models/dataset/dask_dataset.py b/cdisc_rules_engine/models/dataset/dask_dataset.py
index e338b09f3..2663ae9fd 100644
--- a/cdisc_rules_engine/models/dataset/dask_dataset.py
+++ b/cdisc_rules_engine/models/dataset/dask_dataset.py
@@ -343,16 +343,14 @@ def iloc(self, n=None, column=None):
     def fillna(
         self,
         value=None,
-        method=None,
         axis=None,
         inplace=False,
         limit=None,
-        downcast=None,
     ):
         """
         Fill NA/NaN values using the specified method.
         """
-        result = self._data.fillna(value=value, method=method, axis=axis, limit=limit)
+        result = self._data.fillna(value=value, axis=axis, limit=limit)
         if inplace:
             self._data = result
             return None
diff --git a/cdisc_rules_engine/models/dataset/dataset_interface.py b/cdisc_rules_engine/models/dataset/dataset_interface.py
index 4aea0bc01..bd7d8e747 100644
--- a/cdisc_rules_engine/models/dataset/dataset_interface.py
+++ b/cdisc_rules_engine/models/dataset/dataset_interface.py
@@ -229,11 +229,9 @@ def reset_index(self, drop=False, **kwargs):
     def fillna(
         self,
         value=None,
-        method=None,
         axis=None,
         inplace=False,
         limit=None,
-        downcast=None,
     ):
         """
         Fill NA/NaN values using the specified method.
diff --git a/cdisc_rules_engine/models/dataset/pandas_dataset.py b/cdisc_rules_engine/models/dataset/pandas_dataset.py
index 7b8f51e3e..dd9962ce6 100644
--- a/cdisc_rules_engine/models/dataset/pandas_dataset.py
+++ b/cdisc_rules_engine/models/dataset/pandas_dataset.py
@@ -260,22 +260,18 @@ def reset_index(self, drop=False, **kwargs):
     def fillna(
         self,
         value=None,
-        method=None,
         axis=None,
         inplace=False,
         limit=None,
-        downcast=None,
     ):
         """
         Fill NA/NaN values using the specified method.
         """
         result = self._data.fillna(
             value=value,
-            method=method,
             axis=axis,
             inplace=inplace,
             limit=limit,
-            downcast=downcast,
         )
         if inplace:
             return None