diff --git a/src/CacheSim/IntMap.elm b/src/CacheSim/IntMap.elm
index 3503671..7511207 100644
--- a/src/CacheSim/IntMap.elm
+++ b/src/CacheSim/IntMap.elm
@@ -21,7 +21,7 @@ intMapUpdate i f m =
     case (i, m) of
         (_, []) -> []
         (0, (x::xs)) -> (f x)::xs
-        (n, (x::xs)) -> intMapUpdate (n-1) f xs
+        (n, (x::xs)) -> x :: intMapUpdate (n-1) f xs
 
 intMapPut : Int -> a -> IntMap a -> IntMap a
 intMapPut i v = intMapUpdate i (\_ -> v)