diff --git a/src/Monolog/Formatter/FlowdockFormatter.php b/src/Monolog/Formatter/FlowdockFormatter.php
index af63d011..5094af3c 100644
--- a/src/Monolog/Formatter/FlowdockFormatter.php
+++ b/src/Monolog/Formatter/FlowdockFormatter.php
@@ -93,10 +93,22 @@ class FlowdockFormatter implements FormatterInterface
      */
     public function getShortMessage($message)
     {
+        static $hasMbString;
+
+        if (null === $hasMbString) {
+            $hasMbString = function_exists('mb_strlen');
+        }
+
         $maxLength = 45;
 
-        if (strlen($message) > $maxLength) {
-            $message = substr($message, 0, $maxLength - 4) . ' ...';
+        if ($hasMbString) {
+            if (mb_strlen($message, 'UTF-8') > $maxLength) {
+                $message = mb_substr($message, 0, $maxLength - 4, 'UTF-8') . ' ...';
+            }
+        } else {
+            if (strlen($message) > $maxLength) {
+                $message = substr($message, 0, $maxLength - 4) . ' ...';
+            }
         }
 
         return $message;