diff --git a/sys/netinet/in.c b/sys/netinet/in.c
index d1dd2b31b6ef..2794fc068f09 100644
--- a/sys/netinet/in.c
+++ b/sys/netinet/in.c
@@ -81,6 +81,12 @@ static void	in_purgemaddrs(struct ifnet *);
 
 static bool	ia_need_loopback_route(const struct in_ifaddr *);
 
+static bool	subnet_addr_is_broadcast = 1;
+
+SYSCTL_BOOL(_net_inet_ip, OID_AUTO, subnet_addr_is_broadcast, CTLFLAG_RW,
+	&subnet_addr_is_broadcast, true,
+	"Treat IPv4 subnet address as a broadcast address");
+
 VNET_DEFINE_STATIC(int, nosameprefix);
 #define	V_nosameprefix			VNET(nosameprefix)
 SYSCTL_INT(_net_inet_ip, OID_AUTO, no_same_prefix, CTLFLAG_VNET | CTLFLAG_RW,
@@ -1137,9 +1143,11 @@ in_ifaddr_broadcast(struct in_addr in, struct in_ifaddr *ia)
 	     /*
 	      * Check for old-style (host 0) broadcast, but
 	      * taking into account that RFC 3021 obsoletes it.
+	      * Also gated by subnet_addr_is_broadcast sysctl.
 	      */
 	    (ia->ia_subnetmask != IN_RFC3021_MASK &&
-	    ntohl(in.s_addr) == ia->ia_subnet)) &&
+	    ntohl(in.s_addr) == ia->ia_subnet &&
+	    subnet_addr_is_broadcast)) &&
 	     /*
 	      * Check for an all one subnetmask. These
 	      * only exist when an interface gets a secondary