diff --git a/src/Url/MetadataUrlTransformer.php b/src/Url/MetadataUrlTransformer.php
index 89ea04a..9142c14 100644
--- a/src/Url/MetadataUrlTransformer.php
+++ b/src/Url/MetadataUrlTransformer.php
@@ -32,7 +32,7 @@ final class MetadataUrlTransformer {
 		if ( $this->looksSerialized( $value ) ) {
 			$unserialized = $this->unserializeValue( $value );
 
-			if ( ! $unserialized['valid'] || is_object( $unserialized['value'] ) ) {
+			if ( ! $unserialized['valid'] || $this->containsObject( $unserialized['value'] ) ) {
 				return $value;
 			}
 
@@ -118,4 +118,25 @@ final class MetadataUrlTransformer {
 
 		return '' !== $trimmed && in_array( $trimmed[0], array( '{', '[' ), true );
 	}
+
+	/**
+	 * @param mixed $value Value to inspect.
+	 */
+	private function containsObject( $value ): bool {
+		if ( is_object( $value ) ) {
+			return true;
+		}
+
+		if ( ! is_array( $value ) ) {
+			return false;
+		}
+
+		foreach ( $value as $item ) {
+			if ( $this->containsObject( $item ) ) {
+				return true;
+			}
+		}
+
+		return false;
+	}
 }
diff --git a/tests/Unit/Url/MetadataUrlTransformerTest.php b/tests/Unit/Url/MetadataUrlTransformerTest.php
index 3995a65..f73fa1c 100644
--- a/tests/Unit/Url/MetadataUrlTransformerTest.php
+++ b/tests/Unit/Url/MetadataUrlTransformerTest.php
@@ -100,6 +100,13 @@ class MetadataUrlTransformerTest extends TestCase {
 		self::assertSame( $value, $transformer->transformValue( $value, $this->mappings() ) );
 	}
 
+	public function test_it_leaves_serialized_payloads_with_nested_objects_unchanged(): void {
+		$transformer = new MetadataUrlTransformer( new UrlTransformer() );
+		$value       = 'a:2:{s:3:"url";s:28:"https://example.test/inside";s:6:"object";O:8:"stdClass":0:{}}';
+
+		self::assertSame( $value, $transformer->transformValue( $value, $this->mappings() ) );
+	}
+
 	public function test_it_leaves_invalid_json_strings_unchanged(): void {
 		$transformer = new MetadataUrlTransformer( new UrlTransformer() );
 		$value       = '{"url":"https://example.test/missing"';