diff --git a/flit/inifile.py b/flit/inifile.py
index 31d016f..8aa434c 100644
--- a/flit/inifile.py
+++ b/flit/inifile.py
@@ -140,8 +140,8 @@ def _validate_config(cp, path):
 
     if 'description-file' in md_sect:
         description_file = path.parent / md_sect.get('description-file')
-        with description_file.open() as f:
-            raw_desc =  f.read()
+        with description_file.open('r', encoding='utf-8') as f:
+            raw_desc = f.read()
         if description_file.suffix == '.md':
             try:
                 import pypandoc