diff --git a/src/Language/Brainfuck/Instruction/Compressed.hs b/src/Language/Brainfuck/Instruction/Compressed.hs
index bf28a1d..24a000a 100644
--- a/src/Language/Brainfuck/Instruction/Compressed.hs
+++ b/src/Language/Brainfuck/Instruction/Compressed.hs
@@ -20,8 +20,10 @@ import Language.Brainfuck.Instruction qualified as Instruction
 data CompressedInstruction
   = Add Word8
   | Subtract Word8
+  -- add and sub wrap when doing more than 255 because Brainfuck operates on u8-cells
   | MoveRight Natural
   | MoveLeft Natural
+  -- disallows moving a negative amount of steps in a direction
   | ReadByte
   | PutByte
   | Loop (Vector CompressedInstruction)
@@ -86,3 +88,7 @@ uncompress = Vector.concatMap uncompressSingle
         ReadByte        -> Vector.singleton Instruction.ReadByte
         Loop      body  -> Vector.singleton $ Instruction.Loop (uncompress body)
 
+-- >>> let source = Vector.replicate 300 Instruction.Increment in source == (uncompress . compress) source
+-- False
+
+