diff --git a/telethon/client/downloads.py b/telethon/client/downloads.py
index ec7e5628..871713c6 100644
--- a/telethon/client/downloads.py
+++ b/telethon/client/downloads.py
@@ -400,7 +400,7 @@ class DownloadMethods(UserMethods):
                 file, 'contact', '.vcard',
                 possible_names=[first_name, phone_number, last_name]
             )
-            f = open(file, 'w', encoding='utf-8')
+            f = open(file, 'wb', encoding='utf-8')
         else:
             f = file