diff --git a/include/haproxy/arg-t.h b/include/haproxy/arg-t.h
index 57b4080ca..d90d326ef 100644
--- a/include/haproxy/arg-t.h
+++ b/include/haproxy/arg-t.h
@@ -83,6 +83,7 @@ enum {
 	ARGC_USRV,     /* use-server message */
 	ARGC_HERR,     /* http-error */
 	ARGC_OT,       /* opentracing scope args */
+	ARGC_OPT,      /* option directive */
 	ARGC_TCO,      /* tcp-request connection expression */
 	ARGC_TSE,      /* tcp-request session expression */
 	ARGC_TRQ,      /* tcp-request content expression */
diff --git a/src/sample.c b/src/sample.c
index 953e463a4..2e04c74c9 100644
--- a/src/sample.c
+++ b/src/sample.c
@@ -1310,6 +1310,7 @@ int smp_resolve_args(struct proxy *p, char **err)
 		case ARGC_USRV:  where = "in use-server or balance expression in"; break;
 		case ARGC_HERR:  where = "in http-error directive in"; break;
 		case ARGC_OT:    where = "in ot-scope directive in"; break;
+		case ARGC_OPT:   where = "in option directive in"; break;
 		case ARGC_TCO:   where = "in tcp-request connection expression in"; break;
 		case ARGC_TSE:   where = "in tcp-request session expression in"; break;
 		case ARGC_TRQ:   where = "in tcp-request content expression in"; break;