diff --git a/harpie.cabal b/harpie.cabal
--- a/harpie.cabal
+++ b/harpie.cabal
@@ -1,6 +1,6 @@
 cabal-version: 3.0
 name: harpie
-version: 0.1.0.0
+version: 0.1.0.1
 license: BSD-3-Clause
 license-file: LICENSE
 copyright: Tony Day (c) 2016-2024
diff --git a/src/Harpie/Fixed.hs b/src/Harpie/Fixed.hs
--- a/src/Harpie/Fixed.hs
+++ b/src/Harpie/Fixed.hs
@@ -1282,7 +1282,7 @@
 -- >>> pretty $ indexes (Dims @[0,1]) (S.UnsafeFins [1,1]) a
 -- [16,17,18,19]
 indexes ::
-  forall ds s s' xs a.
+  forall s' s ds xs a.
   ( KnownNats s,
     KnownNats s',
     s' ~ Eval (DeleteDims ds s),
diff --git a/src/Harpie/Shape.hs b/src/Harpie/Shape.hs
--- a/src/Harpie/Shape.hs
+++ b/src/Harpie/Shape.hs
@@ -981,8 +981,22 @@
 -- 1
 getDim :: Int -> [Int] -> Int
 getDim 0 [] = 1
-getDim i s = fromMaybe (error "getDim outside bounds") (s List.!? i)
+getDim i s = fromMaybe (error "getDim outside bounds") (maybeGetDim s i)
 
+maybeGetDim :: [a] -> Int -> Maybe a
+maybeGetDim xs n
+  | n < 0 = Nothing
+  | otherwise =
+      foldr
+        ( \x r k -> case k of
+            0 -> Just x
+            _ -> r (k - 1)
+        )
+        (const Nothing)
+        xs
+        n
+{-# INLINEABLE maybeGetDim #-}
+
 -- | Get the dimension of a shape at the supplied index. Error if out-of-bounds or non-computable (usually unknown to the compiler).
 --
 -- >>> :k! Eval (GetDim 1 [2,3,4])
@@ -1348,9 +1362,6 @@
 -- >>> :k! Eval (GetLastPositions [2,0] [2,3,4])
 -- ...
 -- = [3, 1]
--- >>> :k! Eval (GetLastPositions '[0] '[0])
--- ...
--- = '[0 GHC.TypeNats.- 1]
 data GetLastPositions :: [Nat] -> [Nat] -> Exp [Nat]
 
 type instance