diff --git a/apps/user_ldap/lib/Configuration.php b/apps/user_ldap/lib/Configuration.php
index 36258f5ad271b..aa2a125d52206 100644
--- a/apps/user_ldap/lib/Configuration.php
+++ b/apps/user_ldap/lib/Configuration.php
@@ -604,6 +604,7 @@ public function getAvatarAttributes(): array {
 	 * Returns TRUE if the ldapHost variable starts with 'ldapi://'
 	 */
 	public function usesLdapi(): bool {
-		return (substr($this->config['ldapHost'], 0, strlen('ldapi://')) === 'ldapi://');
+		$host = $this->config['ldapHost'];
+		return is_string($host) && (substr($host, 0, strlen('ldapi://')) === 'ldapi://');
 	}
 }