diff --git a/programs/fib.as b/programs/fib.as
index acbecfc..bf0cc7d 100644
--- a/programs/fib.as
+++ b/programs/fib.as
@@ -6,15 +6,16 @@ define iterations 13
 
       ldi r1 #0
       ldi r2 #1
-      ldi r3 #0
       ldi r4 iterations
       ldi r7 number_display
 .loop str r3
       cmp r4 r0
       bif zero .done
-      cpy r1 r2
-      cpy r2 r3
-      add r3 r1 r2
+      add r1 r1 r2
+      add r2 r1 r2
+      dec r4 r4
+      cmp r4 r0
+      bif zero .done
       dec r4 r4
       jmp .loop
 .done hlt