diff --git a/src/wp-includes/class-wp-duotone.php b/src/wp-includes/class-wp-duotone.php
index 8666f85a0f8e4..d0b978eacef21 100644
--- a/src/wp-includes/class-wp-duotone.php
+++ b/src/wp-includes/class-wp-duotone.php
@@ -1193,7 +1193,7 @@ public static function restore_image_outer_container( $block_content ) {
 
 		$inner_classnames = explode( ' ', $tags->get_attribute( 'class' ) );
 		foreach ( $inner_classnames as $classname ) {
-			if ( 0 === strpos( $classname, 'wp-duotone' ) ) {
+			if ( str_starts_with( $classname, 'wp-duotone' ) ) {
 				$tags->remove_class( $classname );
 				$tags->seek( 'wrapper-div' );
 				$tags->add_class( $classname );