diff --git a/library/server/wsf/src/wsf_response.e b/library/server/wsf/src/wsf_response.e
index 72be7265..5ec5c0f6 100644
--- a/library/server/wsf/src/wsf_response.e
+++ b/library/server/wsf/src/wsf_response.e
@@ -207,7 +207,7 @@ feature -- Header output operation
 			if header_committed then
 				report_content_already_sent_and_header_ignored
 			else
-				header.append_raw_header_data (a_text)
+				header.put_raw_header_data (a_text)
 			end
 		ensure
 			message_writable: message_writable