diff --git a/src/java/davmail/imap/ImapConnection.java b/src/java/davmail/imap/ImapConnection.java
index 4d8cae30..162d47ad 100644
--- a/src/java/davmail/imap/ImapConnection.java
+++ b/src/java/davmail/imap/ImapConnection.java
@@ -723,7 +723,7 @@ public class ImapConnection extends AbstractConnection {
         sendClient("* " + currentFolder.recent + " RECENT");
     }
 
-    class MessageWrapper {
+    static class MessageWrapper {
         protected OutputStream os;
         protected StringBuilder buffer;
         protected ExchangeSession.Message message;