diff --git a/py/server/deephaven/table.py b/py/server/deephaven/table.py
index 2eca7ae3417..df6cc4b3e93 100644
--- a/py/server/deephaven/table.py
+++ b/py/server/deephaven/table.py
@@ -1102,9 +1102,12 @@ def sort(self, order_by: Union[str, Sequence[str]],
             order_by = to_sequence(order_by)
             if not order:
                 order = (SortDirection.ASCENDING,) * len(order_by)
-            order = to_sequence(order)
-            if len(order_by) != len(order):
-                raise DHError(message="The number of sort columns must be the same as the number of sort directions.")
+            else:
+                order = to_sequence(order)
+                if any([o not in (SortDirection.ASCENDING, SortDirection.DESCENDING) for o in order]):
+                    raise DHError(message="The sort direction must be either 'ASCENDING' or 'DESCENDING'.")
+                if len(order_by) != len(order):
+                    raise DHError(message="The number of sort columns must be the same as the number of sort directions.")
 
             sort_columns = [_sort_column(col, dir_) for col, dir_ in zip(order_by, order)]
             j_sc_list = j_array_list(sort_columns)
@@ -2008,6 +2011,9 @@ def partition_by(self, by: Union[str, Sequence[str]], drop_keys: bool = False) -
             DHError
         """
         try:
+            if not isinstance(drop_keys, bool):
+                raise DHError(message="drop_keys must be a boolean value.")
+
             by = to_sequence(by)
             return PartitionedTable(j_partitioned_table=self.j_table.partitionBy(drop_keys, *by))
         except Exception as e:
@@ -2737,12 +2743,14 @@ def sort(self, order_by: Union[str, Sequence[str]],
             DHError
         """
         try:
-            order_by = to_sequence(order_by)
             if not order:
                 order = (SortDirection.ASCENDING,) * len(order_by)
-            order = to_sequence(order)
-            if len(order_by) != len(order):
-                raise ValueError("The number of sort columns must be the same as the number of sort directions.")
+            else:
+                order = to_sequence(order)
+                if any([o not in (SortDirection.ASCENDING, SortDirection.DESCENDING) for o in order]):
+                    raise DHError(message="The sort direction must be either 'ASCENDING' or 'DESCENDING'.")
+                if len(order_by) != len(order):
+                    raise DHError(message="The number of sort columns must be the same as the number of sort directions.")
 
             sort_columns = [_sort_column(col, dir_) for col, dir_ in zip(order_by, order)]
             j_sc_list = j_array_list(sort_columns)
diff --git a/py/server/tests/test_parquet.py b/py/server/tests/test_parquet.py
index 612d9bbc759..2d49f7c82cd 100644
--- a/py/server/tests/test_parquet.py
+++ b/py/server/tests/test_parquet.py
@@ -658,7 +658,7 @@ def verify_table_from_disk(table):
             self.assertTrue(len(table.columns))
             self.assertTrue(table.columns[0].name == "X")
             self.assertTrue(table.columns[0].column_type == ColumnType.PARTITIONING)
-            self.assert_table_equals(table.select().sort("X", "Y"), source.sort("X", "Y"))
+            self.assert_table_equals(table.select().sort(["X", "Y"]), source.sort(["X", "Y"]))
 
         def verify_file_names():
             partition_dir_path = os.path.join(root_dir, 'X=Aa')
diff --git a/py/server/tests/test_table.py b/py/server/tests/test_table.py
index 5e30966d906..c9abe604a08 100644
--- a/py/server/tests/test_table.py
+++ b/py/server/tests/test_table.py
@@ -1105,6 +1105,16 @@ def my_fn(vals):
             t = partitioned_by_formula()
             self.assertIsNotNone(t)
 
+    def test_arg_validation(self):
+        t = empty_table(1).update(["A=i", "B=i", "C=i"])
+        with self.assertRaises(DHError) as cm:
+            t.sort("A", "B")
+        self.assertIn("The sort direction must be", str(cm.exception))
+
+        with self.assertRaises(DHError) as cm:
+            t.partition_by("A", "B")
+        self.assertIn("drop_keys must be", str(cm.exception))
+
 
 if __name__ == "__main__":
     unittest.main()