diff --git a/zx-brainfuck/main.asm b/zx-brainfuck/main.asm
index 9c206f2..0813466 100644
--- a/zx-brainfuck/main.asm
+++ b/zx-brainfuck/main.asm
@@ -39,7 +39,9 @@ tbl_routines    dw  F_INC_DP, F_DEC_DP, F_INC_VAL, F_DEC_VAL, F_OUT, F_IN, F_JMP
 ; To test the "," operator
 ;src   db  "++++++++++>+[,<.>.]", 0
 ; Bad Boy Hello world - crashes most interpreters
-src   db  ">++++++++[<+++++++++>-]<.>>+>+>++>[-]+<[>[->+<<++++>]<<]>.+++++++..+++.>>+++++++.<<<[[-]<[-]>]<+++++++++++++++.>>.+++.------.--------.>>+.>++++.", 0
+;src   db  ">++++++++[<+++++++++>-]<.>>+>+>++>[-]+<[>[->+<<++++>]<<]>.+++++++..+++.>>+++++++.<<<[[-]<[-]>]<+++++++++++++++.>>.+++.------.--------.>>+.>++++.", 0
+; Fibonacci numbers
+src db ">++++++++++>+>+[[+++++[>++++++++<-]>.<++++++[>--------<-]+<<<]>.>>[[-]<[>+<-]>>[<<+>+>-]<[>+<-[>+<-[>+<-[>+<-[>+<-[>+<-[>+<-[>+<-[>+<-[>[-]>+>+<<<-[>+<-]]]]]]]]]]]+>>>]<<<]", 0
 
 
 start
diff --git a/zx-brainfuck/main.tap b/zx-brainfuck/main.tap
index a92fc0b..5c03b98 100644
Binary files a/zx-brainfuck/main.tap and b/zx-brainfuck/main.tap differ