diff --git a/cost_function.py b/cost_function.py
index f182fc48f4ab46f558af637de388997a1ea593db..7dc58f11392bdee7987684ed3c2121018225eada 100755
--- a/cost_function.py
+++ b/cost_function.py
@@ -13,7 +13,7 @@ Input:
 - shapefiles, specified as command line arguments
 
 Output: the graph of segments with cost functions,
-'segments_cost_functions.gt'
+segments_cost_functions.gt or segments_cost_functions.graphml.
 
 """