diff --git a/ips.cabal b/ips.cabal
index 2527b4a..4ccb050 100644
--- a/ips.cabal
+++ b/ips.cabal
@@ -10,6 +10,7 @@ maintainer: rhiannon morris <rhi@rhiannon.website>
 common deps
   default-language: Haskell2010
   default-extensions:
+    BangPatterns,
     BlockArguments,
     DerivingStrategies,
     DuplicateRecordFields,
diff --git a/src/IPS/Parse.hs b/src/IPS/Parse.hs
index f0f82f4..228fe76 100644
--- a/src/IPS/Parse.hs
+++ b/src/IPS/Parse.hs
@@ -5,7 +5,6 @@ import IPS.Types
 import Data.Attoparsec.ByteString (Parser)
 import qualified Data.Attoparsec.ByteString as Parse
 import Data.Bits
-import Data.Bifunctor
 import qualified Data.ByteString as ByteString
 import Data.Functor
 import qualified Data.Vector.Generic as Vector
@@ -24,7 +23,7 @@ parseBody = uncurry Vector.fromListN <$> go where
   go = eof <|> chunk
   eof = Parse.string "EOF" $> (0, [])
   chunk = liftA2 cons parseChunk go
-    where cons c = bimap (+ 1) (c :)
+    where cons c (!n, cs) = (n + 1, c : cs)
 
 parseChunk :: Parser Chunk
 parseChunk = do
@@ -45,7 +44,7 @@ parseWord24 = parseWordBE 3
 
 parseWordBE :: (Integral a, Bits a) => Word -> Parser a
 parseWordBE = go 0 where
-  go acc 0 = pure acc
-  go acc i = do
+  go !acc 0 = pure acc
+  go !acc i = do
     b <- fromIntegral <$> Parse.anyWord8
     go ((acc `shiftL` 8) .|. b) (i - 1)