diff --git a/buggy.py b/buggy.py
--- a/buggy.py
+++ b/buggy.py
@@ -12,7 +12,7 @@
         def fib(n):
             if Fib[n] != -1:
                 return Fib[n]
-            Fib[n] = fib(n - 1) + fib(n - 1)
+            Fib[n] = fib(n - 1) + fib(n - 2)
             return Fib[n]
 
         if n == 0:
