diff --git a/wp-includes/formatting.php b/wp-includes/formatting.php
index f91c239422..20442146a5 100644
--- a/wp-includes/formatting.php
+++ b/wp-includes/formatting.php
@@ -1324,7 +1324,7 @@ function wp_trim_excerpt($text) {
 		$text = apply_filters('the_content', $text);
 		$text = str_replace(']]>', ']]>', $text);
 		$text = strip_tags($text);
-		$excerpt_length = 55;
+		$excerpt_length = apply_filters('excerpt_length', 55);
 		$words = explode(' ', $text, $excerpt_length + 1);
 		if (count($words) > $excerpt_length) {
 			array_pop($words);