diff --git a/apps/dav/appinfo/v1/caldav.php b/apps/dav/appinfo/v1/caldav.php
index 333e8bbb3c..3e56e3d0e8 100644
--- a/apps/dav/appinfo/v1/caldav.php
+++ b/apps/dav/appinfo/v1/caldav.php
@@ -62,7 +62,10 @@ $server->setBaseUri($baseuri);
 $server->addPlugin(new MaintenancePlugin());
 $server->addPlugin(new \Sabre\DAV\Auth\Plugin($authBackend, 'ownCloud'));
 $server->addPlugin(new \Sabre\CalDAV\Plugin());
-$server->addPlugin(new \Sabre\DAVACL\Plugin());
+
+$acl = new \OCA\DAV\Connector\LegacyDAVACL();
+$server->addPlugin($acl);
+
 $server->addPlugin(new \Sabre\CalDAV\ICSExportPlugin());
 $server->addPlugin(new ExceptionLoggerPlugin('caldav', \OC::$server->getLogger()));
 
diff --git a/apps/dav/appinfo/v1/carddav.php b/apps/dav/appinfo/v1/carddav.php
index 54f0d259bb..4a3f98475c 100644
--- a/apps/dav/appinfo/v1/carddav.php
+++ b/apps/dav/appinfo/v1/carddav.php
@@ -22,7 +22,6 @@
 // Backends
 use OCA\DAV\CardDAV\AddressBookRoot;
 use OCA\DAV\CardDAV\CardDavBackend;
-use OCA\DAV\Connector\Sabre\AppEnabledPlugin;
 use OCA\DAV\Connector\Sabre\Auth;
 use OCA\DAV\Connector\Sabre\ExceptionLoggerPlugin;
 use OCA\DAV\Connector\Sabre\MaintenancePlugin;
@@ -63,7 +62,10 @@ $server->setBaseUri($baseuri);
 $server->addPlugin(new MaintenancePlugin());
 $server->addPlugin(new \Sabre\DAV\Auth\Plugin($authBackend, 'ownCloud'));
 $server->addPlugin(new Plugin());
-$server->addPlugin(new \Sabre\DAVACL\Plugin());
+
+$acl = new \OCA\DAV\Connector\LegacyDAVACL();
+$server->addPlugin($acl);
+
 $server->addPlugin(new \Sabre\CardDAV\VCFExportPlugin());
 $server->addPlugin(new ExceptionLoggerPlugin('carddav', \OC::$server->getLogger()));
 
diff --git a/apps/dav/lib/caldav/caldavbackend.php b/apps/dav/lib/caldav/caldavbackend.php
index c674876598..7f6810fb1e 100644
--- a/apps/dav/lib/caldav/caldavbackend.php
+++ b/apps/dav/lib/caldav/caldavbackend.php
@@ -138,6 +138,7 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 	 * @return array
 	 */
 	function getCalendarsForUser($principalUri) {
+		$principalUri = $this->convertPrincipal($principalUri, true);
 		$fields = array_values($this->propertyMap);
 		$fields[] = 'id';
 		$fields[] = 'uri';
@@ -164,7 +165,7 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 			$calendar = [
 				'id' => $row['id'],
 				'uri' => $row['uri'],
-				'principaluri' => $row['principaluri'],
+				'principaluri' => $this->convertPrincipal($row['principaluri'], false),
 				'{' . Plugin::NS_CALENDARSERVER . '}getctag' => 'http://sabre.io/ns/sync/' . ($row['synctoken']?$row['synctoken']:'0'),
 				'{http://sabredav.org/ns}sync-token' => $row['synctoken']?$row['synctoken']:'0',
 				'{' . Plugin::NS_CALDAV . '}supported-calendar-component-set' => new SupportedCalendarComponentSet($components),
@@ -1093,7 +1094,7 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 			$newValues = [];
 
 			foreach($mutations as $propertyName=>$propertyValue) {
-			if ($propertyName === '{http://calendarserver.org/ns/}source') {
+				if ($propertyName === '{http://calendarserver.org/ns/}source') {
 					$newValues['source'] = $propertyValue->getHref();
 				} else {
 					$fieldName = $this->subscriptionPropertyMap[$propertyName];
@@ -1373,4 +1374,14 @@ class CalDavBackend extends AbstractBackend implements SyncSupport, Subscription
 		return $this->sharingBackend->applyShareAcl($resourceId, $acl);
 	}
 
+	private function convertPrincipal($principalUri, $toV2) {
+		if ($this->principalBackend->getPrincipalPrefix() === 'principals') {
+			list(, $name) = URLUtil::splitPath($principalUri);
+			if ($toV2 === true) {
+				return "principals/users/$name";
+			}
+			return "principals/$name";
+		}
+		return $principalUri;
+	}
 }
diff --git a/apps/dav/lib/connector/legacydavacl.php b/apps/dav/lib/connector/legacydavacl.php
new file mode 100644
index 0000000000..149bd85e4b
--- /dev/null
+++ b/apps/dav/lib/connector/legacydavacl.php
@@ -0,0 +1,69 @@
+<?php
+/**
+ * @author Joas Schilling <nickvergessen@owncloud.com>
+ *
+ * @copyright Copyright (c) 2016, ownCloud, Inc.
+ * @license AGPL-3.0
+ *
+ * This code is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3,
+ * as published by the Free Software Foundation.
+ *
+ * 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 Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License, version 3,
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ *
+ */
+
+namespace OCA\DAV\Connector;
+
+
+use Sabre\HTTP\URLUtil;
+
+class LegacyDAVACL extends \Sabre\DAVACL\Plugin {
+
+	/**
+	 * Converts the v1 principal `principal/<username>` to the new v2
+	 * `principal/users/<username>` which is required for permission checks
+	 *
+	 * @inheritdoc
+	 */
+	function getCurrentUserPrincipal() {
+		$principalV1 = parent::getCurrentUserPrincipal();
+		if (is_null($principalV1)) {
+			return $principalV1;
+		}
+		return $this->convertPrincipal($principalV1, true);
+	}
+
+
+	/**
+	 * @inheritdoc
+	 */
+	function getCurrentUserPrincipals() {
+		$principalV2 = $this->getCurrentUserPrincipal();
+
+		if (is_null($principalV2)) return [];
+
+		$principalV1 = $this->convertPrincipal($principalV2, false);
+		return array_merge(
+			[
+				$principalV2,
+				$principalV1
+			],
+			$this->getPrincipalMembership($principalV1)
+		);
+	}
+
+	private function convertPrincipal($principal, $toV2) {
+		list(, $name) = URLUtil::splitPath($principal);
+		if ($toV2) {
+			return "principals/users/$name";
+		}
+		return "principals/$name";
+	}
+}