diff --git a/framework/Mime/lib/Horde/Mime/Part.php b/framework/Mime/lib/Horde/Mime/Part.php
index 93042d5abf7..98797237c56 100644
--- a/framework/Mime/lib/Horde/Mime/Part.php
+++ b/framework/Mime/lib/Horde/Mime/Part.php
@@ -294,7 +294,9 @@ public function __clone()
             $this->_contentTypeParams->getArrayCopy()
         );
 
-        $this->_contents = $this->_writeStream($this->_contents);
+        if (!empty($this->_contents)) {
+            $this->_contents = $this->_writeStream($this->_contents);
+        }
     }
 
     /**