diff -Naru IMAPClient-0.5.2/imapclient/imapclient.py IMAPClient-0.5.2-fix/imapclient/imapclient.py
--- IMAPClient-0.5.2/imapclient/imapclient.py	2010-01-25 02:17:51.000000000 +0900
+++ IMAPClient-0.5.2-fix/imapclient/imapclient.py	2010-05-02 17:44:18.000000000 +0900
@@ -574,8 +574,9 @@
 
             if msgid != None:
                 # Response for a new message
-                current_msg_data = {}
-                out[msgid] = current_msg_data
+                if msgid not in out:
+                    out[msgid] = {}
+                current_msg_data = out[msgid]
 
             current_msg_data.update(data)