diff --git a/apps/encryption/tests/Crypto/EncryptAllTest.php b/apps/encryption/tests/Crypto/EncryptAllTest.php
index b99e9144be8..459f680a374 100644
--- a/apps/encryption/tests/Crypto/EncryptAllTest.php
+++ b/apps/encryption/tests/Crypto/EncryptAllTest.php
@@ -121,6 +121,7 @@ class EncryptAllTest extends TestCase {
 
 		/* We need format method to return a string */
 		$outputFormatter = $this->createMock(OutputFormatterInterface::class);
+		$outputFormatter->method('isDecorated')->willReturn(false);
 		$outputFormatter->method('format')->willReturnArgument(0);
 
 		$this->outputInterface->expects($this->any())->method('getFormatter')
@@ -346,9 +347,11 @@ class EncryptAllTest extends TestCase {
 				['/user1/files/foo/subfile'],
 			);
 
+		$outputFormatter = $this->createMock(OutputFormatterInterface::class);
+		$outputFormatter->method('isDecorated')->willReturn(false);
 		$this->outputInterface->expects($this->any())
 			->method('getFormatter')
-			->willReturn($this->createMock(OutputFormatterInterface::class));
+			->willReturn($outputFormatter);
 		$progressBar = new ProgressBar($this->outputInterface);
 
 		$this->invokePrivate($encryptAll, 'encryptUsersFiles', ['user1', $progressBar, '']);
diff --git a/lib/private/Console/TimestampFormatter.php b/lib/private/Console/TimestampFormatter.php
index c25ed578805..8d74c28e94f 100644
--- a/lib/private/Console/TimestampFormatter.php
+++ b/lib/private/Console/TimestampFormatter.php
@@ -94,11 +94,11 @@ class TimestampFormatter implements OutputFormatterInterface {
 	/**
 	 * Formats a message according to the given styles.
 	 *
-	 * @param string $message The message to style
-	 * @return string The styled message, prepended with a timestamp using the
+	 * @param string|null $message The message to style
+	 * @return string|null The styled message, prepended with a timestamp using the
 	 * log timezone and dateformat, e.g. "2015-06-23T17:24:37+02:00"
 	 */
-	public function format($message) {
+	public function format(?string $message): ?string {
 		if (!$this->formatter->isDecorated()) {
 			// Don't add anything to the output when we shouldn't
 			return $this->formatter->format($message);
diff --git a/tests/Core/Command/Encryption/ChangeKeyStorageRootTest.php b/tests/Core/Command/Encryption/ChangeKeyStorageRootTest.php
index 1d5e2ac420d..ecb3faaa25d 100644
--- a/tests/Core/Command/Encryption/ChangeKeyStorageRootTest.php
+++ b/tests/Core/Command/Encryption/ChangeKeyStorageRootTest.php
@@ -75,6 +75,7 @@ class ChangeKeyStorageRootTest extends TestCase {
 
 		/* We need format method to return a string */
 		$outputFormatter = $this->createMock(OutputFormatterInterface::class);
+		$outputFormatter->method('isDecorated')->willReturn(false);
 		$outputFormatter->method('format')->willReturnArgument(0);
 
 		$this->outputInterface->expects($this->any())->method('getFormatter')
diff --git a/tests/Core/Command/Preview/RepairTest.php b/tests/Core/Command/Preview/RepairTest.php
index d235c0d0aea..090e9cc0bd0 100644
--- a/tests/Core/Command/Preview/RepairTest.php
+++ b/tests/Core/Command/Preview/RepairTest.php
@@ -71,6 +71,7 @@ class RepairTest extends TestCase {
 
 		/* We need format method to return a string */
 		$outputFormatter = $this->createMock(OutputFormatterInterface::class);
+		$outputFormatter->method('isDecorated')->willReturn(false);
 		$outputFormatter->method('format')->willReturnArgument(0);
 
 		$this->output->expects($this->any())
diff --git a/tests/lib/Encryption/DecryptAllTest.php b/tests/lib/Encryption/DecryptAllTest.php
index f33f88eb214..69f78f435cf 100644
--- a/tests/lib/Encryption/DecryptAllTest.php
+++ b/tests/lib/Encryption/DecryptAllTest.php
@@ -77,12 +77,15 @@ class DecryptAllTest extends TestCase {
 			->disableOriginalConstructor()->getMock();
 		$this->outputInterface = $this->getMockBuilder(OutputInterface::class)
 			->disableOriginalConstructor()->getMock();
+		$this->outputInterface->expects($this->any())->method('isDecorated')
+			->willReturn(false);
 		$this->userInterface = $this->getMockBuilder(UserInterface::class)
 			->disableOriginalConstructor()->getMock();
 
 		/* We need format method to return a string */
 		$outputFormatter = $this->createMock(OutputFormatterInterface::class);
 		$outputFormatter->method('format')->willReturn('foo');
+		$outputFormatter->method('isDecorated')->willReturn(false);
 
 		$this->outputInterface->expects($this->any())->method('getFormatter')
 			->willReturn($outputFormatter);
@@ -304,6 +307,7 @@ class DecryptAllTest extends TestCase {
 
 		/* We need format method to return a string */
 		$outputFormatter = $this->createMock(OutputFormatterInterface::class);
+		$outputFormatter->method('isDecorated')->willReturn(false);
 		$outputFormatter->method('format')->willReturn('foo');
 
 		$output = $this->createMock(OutputInterface::class);