diff --git a/lib/messages/moddn_request.js b/lib/messages/moddn_request.js
index 76052b5..ee6a6cf 100644
--- a/lib/messages/moddn_request.js
+++ b/lib/messages/moddn_request.js
@@ -68,13 +68,21 @@ ModifyDNRequest.prototype._parse = function (ber) {
 
 
 ModifyDNRequest.prototype._toBer = function (ber) {
-  assert.ok(ber);
+  //assert.ok(ber);
 
   ber.writeString(this.entry.toString());
   ber.writeString(this.newRdn.toString());
   ber.writeBoolean(this.deleteOldRdn);
-  if (this.newSuperior)
-    ber.writeString(this.newSuperior.toString());
+  if (this.newSuperior) {
+    var s = this.newSuperior.toString();
+    var len = Buffer.byteLength(s);
+
+    ber.writeByte(0x80); // MODIFY_DN_REQUEST_NEW_SUPERIOR_TAG
+    ber.writeByte(len);
+    ber._ensure(len);
+    ber._buf.write(s, ber._offset);
+    ber._offset += len;
+  } 
 
   return ber;
 };