diff --git a/library/PrimitiveExtras/SmallArray.hs b/library/PrimitiveExtras/SmallArray.hs
--- a/library/PrimitiveExtras/SmallArray.hs
+++ b/library/PrimitiveExtras/SmallArray.hs
@@ -70,6 +70,29 @@
       copySmallArray newMa nextIndex array index amountOfFollowingElements
       return newMa
 
+{-# INLINE update #-}
+update :: (a -> a) -> Int -> SmallArray a -> SmallArray a
+update fn index array =
+  let
+    size = sizeofSmallArray array
+    in if size > index && index >= 0
+      then unsafeUpdateWithSize fn index size array
+      else array
+
+{-# INLINE unsafeUpdate #-}
+unsafeUpdate :: (a -> a) -> Int -> SmallArray a -> SmallArray a
+unsafeUpdate fn index array =
+  unsafeUpdateWithSize fn index (sizeofSmallArray array) array
+
+{-# INLINE unsafeUpdateWithSize #-}
+unsafeUpdateWithSize :: (a -> a) -> Int -> Int -> SmallArray a -> SmallArray a
+unsafeUpdateWithSize fn index size array =
+  runST $ do
+    m <- thawSmallArray array 0 size
+    element <- readSmallArray m index
+    writeSmallArray m index $! fn element
+    unsafeFreezeSmallArray m
+
 {-# INLINE cons #-}
 cons :: a -> SmallArray a -> SmallArray a
 cons a array =
diff --git a/library/PrimitiveExtras/SparseSmallArray.hs b/library/PrimitiveExtras/SparseSmallArray.hs
--- a/library/PrimitiveExtras/SparseSmallArray.hs
+++ b/library/PrimitiveExtras/SparseSmallArray.hs
@@ -89,6 +89,15 @@
     sparseIndex = Bitmap.populatedIndex i b
     in SparseSmallArray b (SmallArray.set sparseIndex e a)
 
+{-# INLINE update #-}
+update :: (e -> e) -> Int -> SparseSmallArray e -> SparseSmallArray e
+update fn i (SparseSmallArray b a) =
+  let
+    sparseIndex = Bitmap.populatedIndex i b
+    in
+      SparseSmallArray b
+        (SmallArray.unsafeUpdate fn sparseIndex a)
+
 -- |
 -- Remove an element.
 {-# INLINE unset #-}
diff --git a/library/PrimitiveExtras/Types.hs b/library/PrimitiveExtras/Types.hs
--- a/library/PrimitiveExtras/Types.hs
+++ b/library/PrimitiveExtras/Types.hs
@@ -10,7 +10,7 @@
 An immutable space-efficient sparse array, 
 which can only store not more than 32 or 64 elements depending on the system architecure.
 -}
-data SparseSmallArray e = SparseSmallArray !Bitmap !(SmallArray e)
+data SparseSmallArray e = SparseSmallArray {-# UNPACK #-} !Bitmap {-# UNPACK #-} !(SmallArray e)
 
 {-|
 A word-size set of ints.
diff --git a/primitive-extras.cabal b/primitive-extras.cabal
--- a/primitive-extras.cabal
+++ b/primitive-extras.cabal
@@ -1,5 +1,5 @@
 name: primitive-extras
-version: 0.8
+version: 0.8.1
 category: Primitive
 synopsis: Extras for the "primitive" library
 homepage: https://github.com/metrix-ai/primitive-extras