diff --git a/6/tuningtrouble.py b/6/tuningtrouble.py
index c3f256f..21fdd69 100644
--- a/6/tuningtrouble.py
+++ b/6/tuningtrouble.py
@@ -2,7 +2,7 @@ from aocd.models import Puzzle
 from aocd import submit
 
 
-def get_marker_pos(signal, N):
+def get_marker_pos(signal: str, N: int) -> int:
     """
     iterate over input signal and find the first occurence
     where the set from i to i+N equals N. This means there