diff --git a/src/main/java/org/apache/commons/mail/util/AttachmentDataSource.java b/src/main/java/org/apache/commons/mail/util/AttachmentDataSource.java
index e8298cc0c..afc0e0703 100644
--- a/src/main/java/org/apache/commons/mail/util/AttachmentDataSource.java
+++ b/src/main/java/org/apache/commons/mail/util/AttachmentDataSource.java
@@ -80,7 +80,7 @@ public InputStream getInputStream()
      */
     public OutputStream getOutputStream() throws IOException
     {
-        throw new UnsupportedOperationException("cannot do this");
+        throw new UnsupportedOperationException("getOutputStream()");
     }
 
     /** Gets the content type. */