Implement this check:

https://author-tools.ietf.org/iddiff?url1=draft-ietf-sidrops-aspa-profile-21&url2=draft-ietf-sidrops-aspa-profile-22&difftype=--html

OK?

Index: aspa.c
===================================================================
RCS file: /cvs/src/usr.sbin/rpki-client/aspa.c,v
diff -u -p -r1.41 aspa.c
--- aspa.c	14 Nov 2025 08:30:22 -0000	1.41
+++ aspa.c	7 Feb 2026 12:07:24 -0000
@@ -90,6 +90,11 @@ aspa_parse_providers(const char *fn, str
 		}
 
 		if (i > 0) {
+			if (provider == 0) {
+				warnx("%s: ASPA: invalid mixed AS 0 Provider",
+				    fn);
+				return 0;
+			}
 			if (aspa->providers[i - 1] > provider) {
 				warnx("%s: ASPA: invalid ProviderASSet order",
 				    fn);