diff --git a/include/types/server.h b/include/types/server.h
index bca7c43f1..70e621a8d 100644
--- a/include/types/server.h
+++ b/include/types/server.h
@@ -206,7 +206,7 @@ struct server {
 	char *rdr_pfx;				/* the redirection prefix */
 
 	struct proxy *proxy;			/* the proxy this server belongs to */
-	struct mux_proto_list *mux_proto;       /* the mux to use for all outgoing connections (specified by the "proto" keyword) */
+	const struct mux_proto_list *mux_proto;       /* the mux to use for all outgoing connections (specified by the "proto" keyword) */
 	int served;				/* # of active sessions currently being served (ie not pending) */
 	int cur_sess;				/* number of currently active sessions (including syn_sent) */
 	unsigned maxconn, minconn;		/* max # of active sessions (0 = unlimited), min# for dynamic limit. */