diff --git a/CHANGELOG b/CHANGELOG
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,5 +1,8 @@
 # Changelog
 
+- 0.2.1 (2025-06-21)
+  * Minor performance improvements and internal housekeeping.
+
 - 0.2.0 (2025-02-18)
   * The base58check encode and decode functions no longer treat version
     bytes (of which there may now be several) in any special fashion.
diff --git a/bench/Main.hs b/bench/Main.hs
--- a/bench/Main.hs
+++ b/bench/Main.hs
@@ -8,11 +8,11 @@
 
 main :: IO ()
 main = defaultMain [
-    base32
+    base58
   ]
 
-base32 :: Benchmark
-base32 = bgroup "ppad-base32" [
+base58 :: Benchmark
+base58 = bgroup "ppad-base58" [
     bgroup "base58" [
       bgroup "encode" [
         bench "hello world" $ nf B58.encode "hello world"
diff --git a/lib/Data/ByteString/Base58.hs b/lib/Data/ByteString/Base58.hs
--- a/lib/Data/ByteString/Base58.hs
+++ b/lib/Data/ByteString/Base58.hs
@@ -20,11 +20,24 @@
 import Data.Bits ((.|.))
 import qualified Data.ByteString as BS
 import qualified Data.ByteString.Unsafe as BU
+import Data.Word (Word8)
 
 fi :: (Integral a, Num b) => a -> b
 fi = fromIntegral
 {-# INLINE fi #-}
 
+-- word8 base58 character to word6 (ish)
+word6 :: Word8 -> Maybe Word8
+word6 c
+  | c >= 49  && c <= 57  = pure $! c - 49 -- 1–9
+  | c >= 65  && c <= 72  = pure $! c - 56 -- A–H
+  | c >= 74  && c <= 78  = pure $! c - 57 -- J–N
+  | c >= 80  && c <= 90  = pure $! c - 58 -- P–Z
+  | c >= 97  && c <= 107 = pure $! c - 64 -- a–k
+  | c >= 109 && c <= 122 = pure $! c - 65 -- m–z
+  | otherwise = Nothing
+{-# INLINE word6 #-}
+
 -- | Encode a base256 'ByteString' as base58.
 --
 --   >>> encode "hello world"
@@ -101,8 +114,8 @@
 -- from base58
 roll_base58 :: BS.ByteString -> Integer
 roll_base58 bs = BS.foldl' alg 0 bs where
-  alg !b !a = case BS.elemIndex a base58_charset of
+  alg !b !a = case word6 a of
     Just w -> b * 58 + fi w
     Nothing ->
-      error "ppad-base58 (roll_base58): not a base58-encoded bytestring"
+      error "ppad-base58 (roll_base58): internal error"
 
diff --git a/ppad-base58.cabal b/ppad-base58.cabal
--- a/ppad-base58.cabal
+++ b/ppad-base58.cabal
@@ -1,6 +1,6 @@
 cabal-version:      3.0
 name:               ppad-base58
-version:            0.2.0
+version:            0.2.1
 synopsis:           base58 and base58check encoding/decoding.
 license:            MIT
 license-file:       LICENSE