diff --git a/src/Command/CKEditorInstallerCommand.php b/src/Command/CKEditorInstallerCommand.php
index cfaae542..9863c627 100644
--- a/src/Command/CKEditorInstallerCommand.php
+++ b/src/Command/CKEditorInstallerCommand.php
@@ -290,8 +290,8 @@ private function info(string $message, OutputInterface $output): void
     private function block(
         string $message,
         OutputInterface $output,
-        string $background = null,
-        string $font = null
+        ?string $background = null,
+        ?string $font = null
     ): void {
         $options = [];