diff --git a/exercises/flatten-array/flatten_array.py b/exercises/flatten-array/flatten_array.py
index 02485969f5..db774c8e25 100644
--- a/exercises/flatten-array/flatten_array.py
+++ b/exercises/flatten-array/flatten_array.py
@@ -1,2 +1,2 @@
-def flatten():
+def flatten(iterable):
     pass