diff --git a/ui/include/events.inc.php b/ui/include/events.inc.php
index 4229485..50a6092 100644
--- a/ui/include/events.inc.php
+++ b/ui/include/events.inc.php
@@ -565,7 +565,7 @@ function getTagString(array $tag, $tag_name_format = PROBLEMS_TAG_NAME_FULL) {
 			return $tag['value'];
 
 		case PROBLEMS_TAG_NAME_SHORTENED:
-			return substr($tag['tag'], 0, 3).(($tag['value'] === '') ? '' : ': '.$tag['value']);
+			return mb_substr($tag['tag'], 0, 3).(($tag['value'] === '') ? '' : ': '.$tag['value']);
 
 		default:
 			return $tag['tag'].(($tag['value'] === '') ? '' : ': '.$tag['value']);