diff --git a/2019/day9/Intcode.hs b/2019/day9/Intcode.hs
index fcbd2c5..94bb100 100644
--- a/2019/day9/Intcode.hs
+++ b/2019/day9/Intcode.hs
@@ -46,12 +46,6 @@ data TuringMachine =
     }
   deriving (Show)
 
-data IntcodeExcept =
-  UnknownOpCodeException
-  deriving (Show)
-
-instance Exception IntcodeExcept
-
 tapePreprocess :: Vector Integer -> Vector Integer
 tapePreprocess t = (V.++) t $ V.replicate 105 0
 
@@ -124,7 +118,7 @@ step tm =
              else 0)
     "9" -> tmn {pointerOffset = pointerOffset tm + (params ! 0)}
     "99" -> tm {state = Halt}
-    _ -> throw UnknownOpCodeException
+    _ -> error "Illegal Opcode."
   where
     pNew = pointer tm + opLength (tape tm ! fromInteger (pointer tm))
     tmn = tm {pointer = pNew}