diff --git a/src/Config.php b/src/Config.php
index c8c5156..abfa0c8 100644
--- a/src/Config.php
+++ b/src/Config.php
@@ -325,6 +325,9 @@ public function setDefaultHeaderComment(
         string $packageName,
         array | string $copyright = []
     ) : static {
+        if ($copyright === '') {
+            $copyright = [];
+        }
         $copyright = (array) $copyright;
         $copyrightLines = "\n";
         if ($copyright) {
diff --git a/tests/ConfigTest.php b/tests/ConfigTest.php
index 3581644..5b20dab 100644
--- a/tests/ConfigTest.php
+++ b/tests/ConfigTest.php
@@ -49,6 +49,11 @@ public function testDefaultHeaderComment() : void
         $header = $this->config->getRules()['header_comment']['header'];
         self::assertStringContainsString('Foo Bar', $header);
         self::assertStringNotContainsString('(c)', $header);
+        $this->config->setDefaultHeaderComment('Foo Bar', '');
+        // @phpstan-ignore-next-line
+        $header = $this->config->getRules()['header_comment']['header'];
+        self::assertStringContainsString('Foo Bar', $header);
+        self::assertStringNotContainsString('(c)', $header);
         $this->config->setDefaultHeaderComment('Bazz', 'Acme');
         // @phpstan-ignore-next-line
         $header = $this->config->getRules()['header_comment']['header'];