diff --git a/src/DiffOp/Diff/Diff.php b/src/DiffOp/Diff/Diff.php
index e24e7f4..e4b9dba 100644
--- a/src/DiffOp/Diff/Diff.php
+++ b/src/DiffOp/Diff/Diff.php
@@ -144,6 +144,8 @@ private function preSetElement( $index, DiffOp $value ): bool {
 	 * @since 0.1
 	 *
 	 * @param string $serialization
+	 *
+	 * @return void
 	 */
 	#[\ReturnTypeWillChange]
 	public function unserialize( $serialization ) {
@@ -390,6 +392,8 @@ private function getNewOffset(): int {
 	 * @since 0.1
 	 *
 	 * @param mixed $value
+	 *
+	 * @return void
 	 */
 	#[\ReturnTypeWillChange]
 	public function append( $value ) {
@@ -403,6 +407,8 @@ public function append( $value ) {
 	 *
 	 * @param int|string $index
 	 * @param mixed $value
+	 *
+	 * @return void
 	 */
 	#[\ReturnTypeWillChange]
 	public function offsetSet( $index, $value ) {