createBucket Issue

Hello

I am experiencing an issue with the method CouchbaseClusterManager::createBucket:

FATAL ERROR:
libcouchbase experienced an unrecoverable error and terminates the program
to avoid undefined behavior.
The program should have generated a "corefile" which may used
to gather more information about the problem.
If your system doesn't create "corefiles" I can tell you that the
assertion failed in /tmp/buildd/libcouchbase-2.5.4/src/bucketconfig/confmon.c at line 293

Here is the PHP code:
{{$adminUsername = 'Administrator';
$adminPassword = 'mySuperP@ssw0rd';
$cluster = new \CouchbaseCluster('couchbase://localhost', $adminUsername, $adminPassword);
$bucketManager = $cluster->manager($adminUsername, $adminPassword);

$bucketManager->createBucket('plop', [
'authType' => 'sasl',
'bucketType' => 'couchbase',
'flushEnabled' => true,
'ramQuotaMB' => 200
]);}}

The documentation of the PHP client does not mention anything about the method options. So I tried to use the options described in the REST API documentation.

System informations:

OS: Ubuntu 14.04
libcouchbase-dev: 2.5.4-1 (from the APT repository)
php couchbase extension: built from sources (dev-master)
php version: 5.6.16-1 from the Ondrej PPA (http://ppa.launchpad.net/ondrej/php5-5.6/ubuntu)
Thank you for your help.