diff --git a/src/lajittelualgoritmit_ilman_analyysia.py b/src/lajittelualgoritmit_ilman_analyysia.py
index 03876441657cd4338445a10662f6cb85369869b1..33f010cb02a5e3a2d136d997caaf038e5e860cb4 100644
--- a/src/lajittelualgoritmit_ilman_analyysia.py
+++ b/src/lajittelualgoritmit_ilman_analyysia.py
@@ -84,6 +84,7 @@ def merge_sort(A):
     right = merge_sort(A[middle:])
     
     A[:] = _merge(left,right)
+    return A
 
 
 """