diff --git a/app/Assembler.hs b/app/Assembler.hs
index da159f3..fe4aa1c 100644
--- a/app/Assembler.hs
+++ b/app/Assembler.hs
@@ -18,6 +18,9 @@ import Compiler
 
 type Bytecode = BL.ByteString
 
+version1 :: Bu.Builder
+version1 = P.execPut $ B.putWord8 1
+
 toBinary :: Command -> P.Put
 toBinary (Const i) = do
     P.putWord8 0x0001
@@ -28,4 +31,4 @@ toBinary Mult = P.putWord8 0x0006
 toBinary Div  = P.putWord8 0x0007
 
 assemble :: [Command] -> Bytecode
-assemble cmds = Bu.toLazyByteString $ mconcat (map (P.execPut . toBinary) cmds)
+assemble cmds = Bu.toLazyByteString $ mconcat $ version1:map (P.execPut . toBinary) cmds