diff --git a/inc/classes/class-imagify-files-iterator.php b/inc/classes/class-imagify-files-iterator.php
index e6904bd80..9e6c2dec8 100644
--- a/inc/classes/class-imagify-files-iterator.php
+++ b/inc/classes/class-imagify-files-iterator.php
@@ -62,7 +62,7 @@ public function __construct( $iterator, $include_folders = true ) {
 	 *
 	 * @return bool Returns whether the current element of the iterator is acceptable through this filter.
 	 */
-	public function accept() {
+	public function accept(): bool {
 		static $extensions, $has_extension_method;
 
 		$file_path = $this->current()->getPathname();
diff --git a/inc/classes/class-imagify-files-recursive-iterator.php b/inc/classes/class-imagify-files-recursive-iterator.php
index e1375a7ab..9246218d2 100644
--- a/inc/classes/class-imagify-files-recursive-iterator.php
+++ b/inc/classes/class-imagify-files-recursive-iterator.php
@@ -52,7 +52,7 @@ public function __construct( $iterator ) {
 	 *
 	 * @return bool Returns whether the current element of the iterator is acceptable through this filter.
 	 */
-	public function accept() {
+	public function accept(): bool {
 		static $extensions, $has_extension_method;
 
 		$file_path = $this->current()->getPathname();