diff --git a/lib/moodlelib.php b/lib/moodlelib.php
index 4a9c1539593..867464fcc76 100644
--- a/lib/moodlelib.php
+++ b/lib/moodlelib.php
@@ -8850,7 +8850,7 @@ function shorten_text($text, $ideal=30, $exact = false, $ending='...') {
     global $CFG;
 
     // if the plain text is shorter than the maximum length, return the whole text
-    if (strlen(preg_replace('/<.*?>/', '', $text)) <= $ideal) {
+    if (textlib::strlen(preg_replace('/<.*?>/', '', $text)) <= $ideal) {
         return $text;
     }
 
@@ -8858,7 +8858,7 @@ function shorten_text($text, $ideal=30, $exact = false, $ending='...') {
     // and only tag in its 'line'
     preg_match_all('/(<.+?>)?([^<>]*)/s', $text, $lines, PREG_SET_ORDER);
 
-    $total_length = strlen($ending);
+    $total_length = textlib::strlen($ending);
     $truncate = '';
 
     // This array stores information about open and close tags and their position
@@ -8877,19 +8877,19 @@ function shorten_text($text, $ideal=30, $exact = false, $ending='...') {
             } else if (preg_match('/^<\s*\/([^\s]+?)\s*>$/s', $line_matchings[1], $tag_matchings)) {
                 // record closing tag
                 $tagdetails[] = (object)array('open'=>false,
-                    'tag'=>strtolower($tag_matchings[1]), 'pos'=>strlen($truncate));
+                    'tag'=>textlib::strtolower($tag_matchings[1]), 'pos'=>textlib::strlen($truncate));
             // if tag is an opening tag (f.e. <b>)
             } else if (preg_match('/^<\s*([^\s>!]+).*?>$/s', $line_matchings[1], $tag_matchings)) {
                 // record opening tag
                 $tagdetails[] = (object)array('open'=>true,
-                    'tag'=>strtolower($tag_matchings[1]), 'pos'=>strlen($truncate));
+                    'tag'=>textlib::strtolower($tag_matchings[1]), 'pos'=>textlib::strlen($truncate));
             }
             // add html-tag to $truncate'd text
             $truncate .= $line_matchings[1];
         }
 
         // calculate the length of the plain text part of the line; handle entities as one character
-        $content_length = strlen(preg_replace('/&[0-9a-z]{2,8};|&#[0-9]{1,7};|&#x[0-9a-f]{1,6};/i', ' ', $line_matchings[2]));
+        $content_length = textlib::strlen(preg_replace('/&[0-9a-z]{2,8};|&#[0-9]{1,7};|&#x[0-9a-f]{1,6};/i', ' ', $line_matchings[2]));
         if ($total_length+$content_length > $ideal) {
             // the number of characters which are left
             $left = $ideal - $total_length;
@@ -8900,14 +8900,14 @@ function shorten_text($text, $ideal=30, $exact = false, $ending='...') {
                 foreach ($entities[0] as $entity) {
                     if ($entity[1]+1-$entities_length <= $left) {
                         $left--;
-                        $entities_length += strlen($entity[0]);
+                        $entities_length += textlib::strlen($entity[0]);
                     } else {
                         // no more characters left
                         break;
                     }
                 }
             }
-            $truncate .= substr($line_matchings[2], 0, $left+$entities_length);
+            $truncate .= textlib::substr($line_matchings[2], 0, $left+$entities_length);
             // maximum length is reached, so get off the loop
             break;
         } else {
@@ -8924,21 +8924,21 @@ function shorten_text($text, $ideal=30, $exact = false, $ending='...') {
     // if the words shouldn't be cut in the middle...
     if (!$exact) {
         // ...search the last occurence of a space...
-        for ($k=strlen($truncate);$k>0;$k--) {
-            if (!empty($truncate[$k]) && ($char = $truncate[$k])) {
-                if ($char == '.' or $char == ' ') {
+        for ($k=textlib::strlen($truncate);$k>0;$k--) {
+            if ($char = textlib::substr($truncate, $k, 1)) {
+                if ($char === '.' or $char === ' ') {
                     $breakpos = $k+1;
                     break;
-                } else if (ord($char) >= 0xE0) {  // Chinese/Japanese/Korean text
-                    $breakpos = $k;               // can be truncated at any UTF-8
-                    break;                        // character boundary.
+                } else if (strlen($char) > 2) {  // Chinese/Japanese/Korean text
+                    $breakpos = $k+1;            // can be truncated at any UTF-8
+                    break;                       // character boundary.
                 }
             }
         }
 
         if (isset($breakpos)) {
             // ...and cut the text in this position
-            $truncate = substr($truncate, 0, $breakpos);
+            $truncate = textlib::substr($truncate, 0, $breakpos);
         }
     }
 
diff --git a/lib/simpletest/testmoodlelib.php b/lib/simpletest/testmoodlelib.php
index 575238fb94c..3a2bd3e001d 100644
--- a/lib/simpletest/testmoodlelib.php
+++ b/lib/simpletest/testmoodlelib.php
@@ -953,6 +953,37 @@ class moodlelib_test extends UnitTestCase {
         $text = "<h1>123456789</h1>";//a string with no convenient breaks
         $this->assertEqual("<h1>12345...</h1>",
             shorten_text($text, 8));
+
+        // ==== this must work with UTF-8 too! ======
+
+        // text without tags
+        $text = "Žluťoučký koníček přeskočil";
+        $this->assertEqual($text, shorten_text($text)); // 30 chars by default
+        $this->assertEqual("Žluťoučký koníče...", shorten_text($text, 19, true));
+        $this->assertEqual("Žluťoučký ...", shorten_text($text, 19, false));
+
+        $text = "<p>Žluťoučký koníček <b>přeskočil</b> potůček</p>";
+        $this->assertEqual($text, shorten_text($text, 60));
+        $this->assertEqual("<p>Žluťoučký koníček ...</p>", shorten_text($text, 21));
+        $this->assertEqual("<p>Žluťoučký koníče...</p>", shorten_text($text, 19, true));
+        $this->assertEqual("<p>Žluťoučký ...</p>", shorten_text($text, 19, false));
+
+        // Japanese
+        $text = '言語設定言語設定abcdefghijkl';
+        $this->assertEqual($text, shorten_text($text)); // 30 chars by default
+        $this->assertEqual("言語設定言語...", shorten_text($text, 9, true));
+        $this->assertEqual("言語設定言語...", shorten_text($text, 9, false));
+        $this->assertEqual("言語設定言語設定ab...", shorten_text($text, 13, true));
+        $this->assertEqual("言語設定言語設定...", shorten_text($text, 13, false));
+
+        // Chinese
+        $text = '简体中文简体中文abcdefghijkl';
+        $this->assertEqual($text, shorten_text($text)); // 30 chars by default
+        $this->assertEqual("简体中文简体...", shorten_text($text, 9, true));
+        $this->assertEqual("简体中文简体...", shorten_text($text, 9, false));
+        $this->assertEqual("简体中文简体中文ab...", shorten_text($text, 13, true));
+        $this->assertEqual("简体中文简体中文...", shorten_text($text, 13, false));
+
     }
 
     function test_usergetdate() {