diff --git a/solutions/src/2023/09.hs b/solutions/src/2023/09.hs
index 2111973..ed1e631 100644
--- a/solutions/src/2023/09.hs
+++ b/solutions/src/2023/09.hs
@@ -41,4 +41,4 @@ nextInSequence :: [Int] -> Int
 nextInSequence = sum . map last . takeWhile (any (0 /=)) . iterate differences
 
 differences :: [Int] -> [Int]
-differences xs = zipWith (-) (tail xs) xs
\ No newline at end of file
+differences xs = zipWith subtract xs (tail xs)
\ No newline at end of file