diff --git a/modoboa/lib/imap_utf7.py b/modoboa/lib/imap_utf7.py
index c8901a9b6..c40348ab8 100644
--- a/modoboa/lib/imap_utf7.py
+++ b/modoboa/lib/imap_utf7.py
@@ -126,7 +126,7 @@ class StreamWriter(codecs.StreamWriter):
 
 
 def imap4_utf_7(name):
-    if name == "imap4-utf-7":
+    if name == "imap4-utf-7" or name == "imap4_utf_7":
         return (encoder, decoder, StreamReader, StreamWriter)