diff --git a/wp-includes/functions.php b/wp-includes/functions.php
index f4c573d7d5..a3a6cc4a8a 100644
--- a/wp-includes/functions.php
+++ b/wp-includes/functions.php
@@ -1342,8 +1342,12 @@ function check_comment($author, $email, $url, $comment, $user_ip) {
 	if ('' == trim( get_settings('moderation_keys') ) ) return true; // If moderation keys are empty
 	$words = explode("\n", get_settings('moderation_keys') );
 	foreach ($words as $word) {
-	$word = trim($word);
-	$pattern = "#$word#i";
+		$word = trim($word);
+
+		// Skip empty lines
+		if (empty($word)) { continue; }
+
+		$pattern = "#$word#i";
 		if ( preg_match($pattern, $author) ) return false;
 		if ( preg_match($pattern, $email) ) return false;
 		if ( preg_match($pattern, $url) ) return false;