diff --git a/program/include/rcube_mime.php b/program/include/rcube_mime.php
index 53655a9cb..e1f736a78 100644
--- a/program/include/rcube_mime.php
+++ b/program/include/rcube_mime.php
@@ -31,7 +31,7 @@
  */
 class rcube_mime
 {
-    private static $default_charset = RCMAIL_CHARSET;
+    private static $default_charset;
 
 
     /**
@@ -39,9 +39,7 @@ class rcube_mime
      */
     function __construct($default_charset = null)
     {
-        if ($default_charset) {
-            self::$default_charset = $default_charset;
-        }
+        self::$default_charset = $default_charset;
     }