diff --git a/db/registrationmapper.php b/db/registrationmapper.php
index 0559af9..58f30ec 100644
--- a/db/registrationmapper.php
+++ b/db/registrationmapper.php
@@ -93,8 +93,9 @@ class RegistrationMapper extends Mapper {
 	 * @param Registration $registration
 	 */
 	public function generateClientSecret(Registration &$registration) {
-		$token = $this->random->generate(32, ISecureRandom::CHAR_HUMAN_READABLE);
+		$token = $this->random->generate(32, "abcdefgijkmnopqrstwxyzABCDEFGHJKLMNPQRSTWXYZ23456789");
+		//FIXME eqivalent to ISecureRandom::CHAR_HUMAN_READABLE introduced in https://github.com/nextcloud/server/commit/f2a2b34e4639e88f8d948a388a51f010212b42a3 but not supported in ownCloud yet. We'll just use the string for now then switch to constants when supported.
 		$registration->setClientSecret($token);
 	}
 
-}
\ No newline at end of file
+}