Index: channels/chan_sip.c
===================================================================
--- channels/chan_sip.c	(revision 408296)
+++ channels/chan_sip.c	(working copy)
@@ -11687,7 +11687,9 @@
 	}
 
 	if ((r = sip_route_list(route, 0, skip))) {
-		add_header(req, "Route", ast_str_buffer(r));
+		if (ast_str_strlen(r)) {
+			add_header(req, "Route", ast_str_buffer(r));
+		}
 		ast_free(r);
 	}
 }