diff --git a/nselib/sip.lua b/nselib/sip.lua
index 9cefaa261..aaab5c43b 100644
--- a/nselib/sip.lua
+++ b/nselib/sip.lua
@@ -63,6 +63,8 @@ Method = {
 Error = {
 	TRYING = 100,
 	RING = 180,
+	BUSY = 486,
+	DECLINE = 603,
 	OK = 200,
 	UNAUTHORIZED = 401,
 	FORBIDDEN = 403,