diff --git a/src/thread/_types.py b/src/thread/_types.py
index 8040d78..6a50a1e 100644
--- a/src/thread/_types.py
+++ b/src/thread/_types.py
@@ -5,7 +5,7 @@
 """
 
 from typing import Any, Literal, Callable, Union
-from typing_extensions import ParamSpec, TypeVar
+from typing_extensions import ParamSpec, TypeVar, Concatenate
 
 
 # Descriptive Types
@@ -34,4 +34,4 @@
 HookFunction = Callable[[_Target_T], Union[Any, None]]
 
 _Dataset_T = TypeVar('_Dataset_T')
-DatasetFunction = Callable[[_Dataset_T], _Target_T]
+DatasetFunction = Callable[Concatenate[_Dataset_T, _Target_P], _Target_T]
diff --git a/src/thread/thread.py b/src/thread/thread.py
index a0017a6..325374e 100644
--- a/src/thread/thread.py
+++ b/src/thread/thread.py
@@ -346,7 +346,7 @@ class ParallelProcessing(Generic[_Target_P, _Target_T, _Dataset_T]):
 
   def __init__(
     self,
-    function: DatasetFunction[_Dataset_T, _Target_T],
+    function: DatasetFunction[_Dataset_T, _Target_P, _Target_T],
     dataset: Sequence[_Dataset_T],
     max_threads: int = 8,
     *overflow_args: Overflow_In,
@@ -507,8 +507,6 @@ def start(self) -> None:
       i: v for i, v in self.overflow_kwargs.items() if i != 'name' and i != 'args'
     }
 
-    print(parsed_args, self.overflow_args)
-
     for i, data_chunk in enumerate(chunk_split(self.dataset, max_threads)):
       chunk_thread = Thread(
         target=self.function,