diff --git a/functions.inc.php b/functions.inc.php
index 8568b2f0..1caa4d21 100644
--- a/functions.inc.php
+++ b/functions.inc.php
@@ -165,7 +165,7 @@ function where($where) {
 
 function process_length($length) {
 	global $enum_length;
-	return (preg_match("~^\\s*(?:$enum_length)(?:\\s*,\\s*(?:$enum_length))*\\s*\$~", $length) && preg_match_all("~$enum_length~", $length, $matches) ? implode(",", $matches[0]) : preg_replace('~[^0-9,]~', '', $length));
+	return (preg_match("~^\\s*(?:$enum_length)(?:\\s*,\\s*(?:$enum_length))*\\s*\$~", $length) && preg_match_all("~$enum_length~", $length, $matches) ? implode(",", $matches[0]) : preg_replace('~[^0-9,+-]~', '', $length));
 }
 
 function collations() {