diff --git a/stdlib/algorithms/insertionsort.codon b/stdlib/algorithms/insertionsort.codon
index b6202fa5..b5732eca 100644
--- a/stdlib/algorithms/insertionsort.codon
+++ b/stdlib/algorithms/insertionsort.codon
@@ -1,32 +1,46 @@
-def _insertion_sort[S,T](arr: Array[T], begin: int, end: int, keyf: Callable[[T], S]):
+# (c) 2022 Exaloop Inc. All rights reserved.
+
+
+def _insertion_sort(
+    arr: Array[T], begin: int, end: int, keyf: Callable[[T], S], T: type, S: type
+) -> void:
     i = begin + 1
     while i < end:
         x = arr[i]
         j = i - 1
         while j >= begin and keyf(x) < keyf(arr[j]):
-            arr[j+1] = arr[j]
+            arr[j + 1] = arr[j]
             j -= 1
-        arr[j+1] = x
+        arr[j + 1] = x
         i += 1
 
-def insertion_sort_array[S,T](collection: Array[T], size: int, keyf: Callable[[T], S]):
+
+def insertion_sort_array(
+    collection: Array[T], size: int, keyf: Callable[[T], S], T: type, S: type
+) -> void:
     """
-        Insertion Sort
-        Sorts the array inplace.
+    Insertion Sort
+    Sorts the array inplace.
     """
     _insertion_sort(collection, 0, size, keyf)
 
-def insertion_sort_inplace[S,T](collection: List[T], keyf: Callable[[T], S]):
+
+def insertion_sort_inplace(
+    collection: List[T], keyf: Callable[[T], S], T: type, S: type
+) -> void:
     """
-        Insertion Sort
-        Sorts the list inplace.
+    Insertion Sort
+    Sorts the list inplace.
     """
     insertion_sort_array(collection.arr, collection.len, keyf)
 
-def insertion_sort[S,T](collection: List[T], keyf: Callable[[T], S]) -> List[T]:
+
+def insertion_sort(
+    collection: List[T], keyf: Callable[[T], S], T: type, S: type
+) -> List[T]:
     """
-        Insertion Sort
-        Returns the sorted list.
+    Insertion Sort
+    Returns the sorted list.
     """
     newlst = copy(collection)
     insertion_sort_inplace(newlst, keyf)