diff --git a/src/Spout/Common/Helper/Escaper/ODS.php b/src/Spout/Common/Helper/Escaper/ODS.php
index b1e27fa..5420836 100644
--- a/src/Spout/Common/Helper/Escaper/ODS.php
+++ b/src/Spout/Common/Helper/Escaper/ODS.php
@@ -22,10 +22,10 @@ class ODS implements EscaperInterface
             // 'ENT_DISALLOWED' ensures that invalid characters in the given document type are replaced.
             // Otherwise control characters like a vertical tab "\v" will make the XML document unreadable by the XML processor
             // @link https://github.com/box/spout/issues/329
-            $replacedString = htmlspecialchars($string, ENT_QUOTES | ENT_DISALLOWED);
+            $replacedString = htmlspecialchars($string, ENT_QUOTES | ENT_DISALLOWED, 'UTF-8');
         } else {
             // We are on hhvm or any other engine that does not support ENT_DISALLOWED.
-            $escapedString =  htmlspecialchars($string, ENT_QUOTES);
+            $escapedString =  htmlspecialchars($string, ENT_QUOTES, 'UTF-8');
 
             // control characters values are from 0 to 1F (hex values) in the ASCII table
             // some characters should not be escaped though: "\t", "\r" and "\n".
diff --git a/src/Spout/Common/Helper/Escaper/XLSX.php b/src/Spout/Common/Helper/Escaper/XLSX.php
index 3885d5e..d72caa8 100644
--- a/src/Spout/Common/Helper/Escaper/XLSX.php
+++ b/src/Spout/Common/Helper/Escaper/XLSX.php
@@ -47,7 +47,7 @@ class XLSX implements EscaperInterface
         $escapedString = $this->escapeControlCharacters($string);
         // @NOTE: Using ENT_QUOTES as XML entities ('<', '>', '&') as well as
         //        single/double quotes (for XML attributes) need to be encoded.
-        $escapedString = htmlspecialchars($escapedString, ENT_QUOTES);
+        $escapedString = htmlspecialchars($escapedString, ENT_QUOTES, 'UTF-8');
 
         return $escapedString;
     }