diff --git a/lib/cli/arguments/Lexer.php b/lib/cli/arguments/Lexer.php
index f6012ef..a5a4767 100644
--- a/lib/cli/arguments/Lexer.php
+++ b/lib/cli/arguments/Lexer.php
@@ -33,6 +33,7 @@ public function __construct(array $items) {
 	 *
 	 * @return string
 	 */
+	#[\ReturnTypeWillChange]
 	public function current() {
 		return $this->_item;
 	}
@@ -49,6 +50,7 @@ public function peek() {
 	/**
 	 * Move the cursor forward 1 element if it is valid.
 	 */
+	#[\ReturnTypeWillChange]
 	public function next() {
 		if ($this->valid()) {
 			$this->_shift();
@@ -60,6 +62,7 @@ public function next() {
 	 *
 	 * @return int
 	 */
+	#[\ReturnTypeWillChange]
 	public function key() {
 		return $this->_index;
 	}
@@ -68,6 +71,7 @@ public function key() {
 	 * Move forward 1 element and, if the method hasn't been called before, reset
 	 * the cursor's position to 0.
 	 */
+	#[\ReturnTypeWillChange]
 	public function rewind() {
 		$this->_shift();
 		if ($this->_first) {
@@ -81,6 +85,7 @@ public function rewind() {
 	 *
 	 * @return bool
 	 */
+	#[\ReturnTypeWillChange]
 	public function valid() {
 		return ($this->_index < $this->_length);
 	}