diff --git a/exercises/prime-factors/prime_factors.py b/exercises/prime-factors/prime_factors.py
index 7a0bdbd012c..aacc9705970 100644
--- a/exercises/prime-factors/prime_factors.py
+++ b/exercises/prime-factors/prime_factors.py
@@ -1,2 +1,2 @@
-def prime_factors():
+def prime_factors(number):
     pass