diff --git a/src/java/davmail/caldav/CaldavConnection.java b/src/java/davmail/caldav/CaldavConnection.java
index 8aabb2e8..386ca209 100644
--- a/src/java/davmail/caldav/CaldavConnection.java
+++ b/src/java/davmail/caldav/CaldavConnection.java
@@ -25,6 +25,7 @@ import davmail.Settings;
 import davmail.exception.DavMailAuthenticationException;
 import davmail.exception.DavMailException;
 import davmail.exception.HttpNotFoundException;
+import davmail.exception.HttpPreconditionFailedException;
 import davmail.exchange.ExchangeSession;
 import davmail.exchange.ExchangeSessionFactory;
 import davmail.exchange.ICSBufferedReader;
@@ -643,7 +644,7 @@ public class CaldavConnection extends AbstractConnection {
     public void patchCalendar(CaldavRequest request) throws IOException {
         String displayname = request.getProperty("displayname");
         String folderPath = request.getFolderPath();
-        if (displayname != null && !folderPath.equalsIgnoreCase("/users/" + session.getEmail() + "/calendar")) {
+        if (displayname != null) {
             String targetPath = request.getParentFolderPath() + '/' + displayname;
             if (!targetPath.equals(folderPath)) {
                 session.moveFolder(folderPath, targetPath);
@@ -1042,6 +1043,8 @@ public class CaldavConnection extends AbstractConnection {
         }
         if (e instanceof HttpNotFoundException) {
             sendErr(HttpStatus.SC_NOT_FOUND, message);
+        } else if (e instanceof HttpPreconditionFailedException) {
+            sendErr(HttpStatus.SC_PRECONDITION_FAILED, message);
         } else {
             sendErr(HttpStatus.SC_SERVICE_UNAVAILABLE, message);
         }
diff --git a/src/java/davmail/exception/HttpPreconditionFailedException.java b/src/java/davmail/exception/HttpPreconditionFailedException.java
new file mode 100644
index 00000000..458452c4
--- /dev/null
+++ b/src/java/davmail/exception/HttpPreconditionFailedException.java
@@ -0,0 +1,35 @@
+/*
+ * DavMail POP/IMAP/SMTP/CalDav/LDAP Exchange Gateway
+ * Copyright (C) 2009  Mickael Guessant
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+package davmail.exception;
+
+import org.apache.commons.httpclient.HttpException;
+
+/**
+ * HttpException with 412 precondition failed status.
+ */
+public class HttpPreconditionFailedException extends HttpException {
+    /**
+     * HttpException with 412 precondition failed status.
+     *
+     * @param message exception message
+     */
+    public HttpPreconditionFailedException(String message) {
+        super(message);
+    }
+}
diff --git a/src/java/davmail/exchange/dav/DavExchangeSession.java b/src/java/davmail/exchange/dav/DavExchangeSession.java
index dd0f4e94..a03eb0ee 100644
--- a/src/java/davmail/exchange/dav/DavExchangeSession.java
+++ b/src/java/davmail/exchange/dav/DavExchangeSession.java
@@ -20,10 +20,7 @@ package davmail.exchange.dav;
 
 import davmail.BundleMessage;
 import davmail.Settings;
-import davmail.exception.DavMailAuthenticationException;
-import davmail.exception.DavMailException;
-import davmail.exception.HttpNotFoundException;
-import davmail.exception.InsufficientStorageException;
+import davmail.exception.*;
 import davmail.exchange.*;
 import davmail.http.DavGatewayHttpClientFacade;
 import davmail.ui.tray.DavGatewayTray;
@@ -1712,9 +1709,12 @@ public class DavExchangeSession extends ExchangeSession {
         try {
             int statusCode = httpClient.executeMethod(method);
             if (statusCode == HttpStatus.SC_PRECONDITION_FAILED) {
-                throw new DavMailException("EXCEPTION_UNABLE_TO_MOVE_FOLDER");
+                throw new HttpPreconditionFailedException(BundleMessage.format("EXCEPTION_UNABLE_TO_MOVE_FOLDER"));
             } else if (statusCode != HttpStatus.SC_CREATED) {
                 throw DavGatewayHttpClientFacade.buildHttpException(method);
+            } else if (folderPath.equalsIgnoreCase("/users/" + getEmail() + "/calendar")) {
+                // calendar renamed, need to reload well known folders 
+                getWellKnownFolders();
             }
         } finally {
             method.releaseConnection();
diff --git a/src/java/davmail/http/DavGatewayHttpClientFacade.java b/src/java/davmail/http/DavGatewayHttpClientFacade.java
index 6bfebaf6..8a7a66f4 100644
--- a/src/java/davmail/http/DavGatewayHttpClientFacade.java
+++ b/src/java/davmail/http/DavGatewayHttpClientFacade.java
@@ -642,6 +642,8 @@ public final class DavGatewayHttpClientFacade {
             return new HttpForbiddenException(message.toString());
         } else if (status == HttpStatus.SC_NOT_FOUND) {
             return new HttpNotFoundException(message.toString());
+        } else if (status == HttpStatus.SC_PRECONDITION_FAILED) {
+            return new HttpPreconditionFailedException(message.toString());
         } else if (status == HttpStatus.SC_INTERNAL_SERVER_ERROR) {
             return new HttpServerErrorException(message.toString());
         } else {