diff --git a/sys/dev/em/if_em.c b/sys/dev/em/if_em.c
index 11fac10796ba..4d615765f12d 100644
--- a/sys/dev/em/if_em.c
+++ b/sys/dev/em/if_em.c
@@ -1609,6 +1609,10 @@ em_setup_interface(device_t dev, struct adapter * adapter)
 		ifp->if_capenable = ifp->if_capabilities;
 	}
 
+	/*
+	 * Tell the upper layer(s) we support long frames.
+	 */
+	ifp->if_data.ifi_hdrlen = sizeof(struct ether_vlan_header);
 #if __FreeBSD_version >= 500000
         ifp->if_capabilities |= IFCAP_VLAN_HWTAGGING | IFCAP_VLAN_MTU;
 #endif