diff --git a/dataformat/excel/classes/writer.php b/dataformat/excel/classes/writer.php
index 0783e9e..94eb669 100644
--- a/dataformat/excel/classes/writer.php
+++ b/dataformat/excel/classes/writer.php
@@ -46,6 +46,13 @@ class writer extends \core\dataformat\spout_base {
     /** @var $spouttype */
     protected $spouttype = \Box\Spout\Common\Type::XLSX;
 
+    /** Set proper encoding for mbstring. **/
+    public function __construct() {
+        if (extension_loaded('mbstring')) {
+            mb_internal_encoding('UTF-8');
+        }
+    }
+
     /**
      * Set the title of the worksheet inside a spreadsheet
      *
@@ -68,4 +75,3 @@ class writer extends \core\dataformat\spout_base {
         $this->sheettitle = $title;
     }
 }
-
diff --git a/dataformat/ods/classes/writer.php b/dataformat/ods/classes/writer.php
index 8f28228..75e4a22 100644
--- a/dataformat/ods/classes/writer.php
+++ b/dataformat/ods/classes/writer.php
@@ -46,6 +46,13 @@ class writer extends \core\dataformat\spout_base {
     /** @var $spouttype */
     protected $spouttype = \Box\Spout\Common\Type::ODS;
 
+    /** Set proper encoding for mbstring. **/
+    public function __construct() {
+        if (extension_loaded('mbstring')) {
+            mb_internal_encoding('UTF-8');
+        }
+    }
+
     /**
      * Set the title of the worksheet inside a spreadsheet
      *