diff --git a/lib/private/server.php b/lib/private/server.php
index b524b3df1b..497f43206f 100644
--- a/lib/private/server.php
+++ b/lib/private/server.php
@@ -786,7 +786,7 @@ class Server extends SimpleContainer implements IServerContainer {
 	 * Get the certificate manager for the user
 	 *
 	 * @param string $uid (optional) if not specified the current loggedin user is used
-	 * @return \OCP\ICertificateManager
+	 * @return \OCP\ICertificateManager | null if $uid is null and no user is logged in
 	 */
 	public function getCertificateManager($uid = null) {
 		if (is_null($uid)) {
diff --git a/lib/public/iservercontainer.php b/lib/public/iservercontainer.php
index 51bd00c6b6..2770280320 100644
--- a/lib/public/iservercontainer.php
+++ b/lib/public/iservercontainer.php
@@ -316,7 +316,7 @@ interface IServerContainer {
 	 * Get the certificate manager for the user
 	 *
 	 * @param string $userId (optional) if not specified the current loggedin user is used
-	 * @return \OCP\ICertificateManager
+	 * @return \OCP\ICertificateManager | null if $userId is null and no user is logged in
 	 * @since 8.0.0
 	 */
 	public function getCertificateManager($userId = null);