diff --git a/docs/add_image_map.py b/docs/add_image_map.py
index 1c9b508eb3..8d6a11e15d 100644
--- a/docs/add_image_map.py
+++ b/docs/add_image_map.py
@@ -35,7 +35,7 @@
 
 print("add image map to " + fileName)
 
-with open(fileName, encoding="utf8") as file:
+with open(fileName) as file:
     lines = file.readlines()
 
 with open(fileName, 'w') as file: