diff --git a/duniterpy/documents/ws2p/heads.py b/duniterpy/documents/ws2p/heads.py
index de359d649bbb366ce2a7f6c7c15e08626b60db8c..ada3a2d9b14bf0d463eb55ddfe6342ac4a87ed98 100644
--- a/duniterpy/documents/ws2p/heads.py
+++ b/duniterpy/documents/ws2p/heads.py
@@ -4,7 +4,7 @@ import re
 from ..block import BlockUID
 from ..constants import ws2p_public_prefix_regex, ws2p_private_prefix_regex,\
     pubkey_regex, signature_regex, ws2pid_regex, block_uid_regex, ws2p_head_regex
-
+from ..document import MalformedDocumentError
 
 @attr.s()
 class API: