diff --git a/core/Command/Background/Ajax.php b/core/Command/Background/Ajax.php
index 5dc94d939d7..41b80eb531f 100644
--- a/core/Command/Background/Ajax.php
+++ b/core/Command/Background/Ajax.php
@@ -26,7 +26,7 @@
 namespace OC\Core\Command\Background;
 
 class Ajax extends Base {
-	protected function getMode() {
+	protected function getMode(): string {
 		return 'ajax';
 	}
 }
diff --git a/core/Command/Background/Base.php b/core/Command/Background/Base.php
index 5b2da21af75..715596f9979 100644
--- a/core/Command/Background/Base.php
+++ b/core/Command/Background/Base.php
@@ -45,7 +45,7 @@ abstract class Base extends Command {
 		parent::__construct();
 	}
 
-	protected function configure() {
+	protected function configure(): void {
 		$mode = $this->getMode();
 		$this
 			->setName("background:$mode")
@@ -59,6 +59,7 @@ abstract class Base extends Command {
 	 *
 	 * @param InputInterface $input
 	 * @param OutputInterface $output
+	 * @return int
 	 */
 	protected function execute(InputInterface $input, OutputInterface $output): int {
 		$mode = $this->getMode();
diff --git a/core/Command/Background/Cron.php b/core/Command/Background/Cron.php
index 9dbb4f855e5..665919b5ae9 100644
--- a/core/Command/Background/Cron.php
+++ b/core/Command/Background/Cron.php
@@ -26,7 +26,7 @@
 namespace OC\Core\Command\Background;
 
 class Cron extends Base {
-	protected function getMode() {
+	protected function getMode(): string {
 		return 'cron';
 	}
 }
diff --git a/core/Command/Background/Job.php b/core/Command/Background/Job.php
index fdfb7484b51..0c64a05e2a7 100644
--- a/core/Command/Background/Job.php
+++ b/core/Command/Background/Job.php
@@ -102,7 +102,7 @@ class Job extends Command {
 		return 0;
 	}
 
-	protected function printJobInfo(int $jobId, IJob $job, OutputInterface$output): void {
+	protected function printJobInfo(int $jobId, IJob $job, OutputInterface $output): void {
 		$row = $this->jobList->getDetailsById($jobId);
 
 		$lastRun = new \DateTime();
diff --git a/core/Command/Background/WebCron.php b/core/Command/Background/WebCron.php
index 7da379b6a53..59bf4746c40 100644
--- a/core/Command/Background/WebCron.php
+++ b/core/Command/Background/WebCron.php
@@ -26,7 +26,7 @@
 namespace OC\Core\Command\Background;
 
 class WebCron extends Base {
-	protected function getMode() {
+	protected function getMode(): string {
 		return 'webcron';
 	}
 }