Index: head/lib/libc/resolv/res_init.c
===================================================================
--- head/lib/libc/resolv/res_init.c
+++ head/lib/libc/resolv/res_init.c
@@ -679,6 +679,8 @@
 		       statp->options |= RES_INSECURE2;
 		} else if (!strncmp(cp, "rotate", sizeof("rotate") - 1)) {
 			statp->options |= RES_ROTATE;
+		} else if (!strncmp(cp, "usevc", sizeof("usevc") - 1)) {
+			statp->options |= RES_USEVC;
 		} else if (!strncmp(cp, "no-check-names",
 				    sizeof("no-check-names") - 1)) {
 			statp->options |= RES_NOCHECKNAME;
Index: head/share/man/man5/resolver.5
===================================================================
--- head/share/man/man5/resolver.5
+++ head/share/man/man5/resolver.5
@@ -28,7 +28,7 @@
 .\"     @(#)resolver.5	8.1 (Berkeley) 6/5/93
 .\" $FreeBSD$
 .\"
-.Dd October 12, 2015
+.Dd August 16, 2018
 .Dt RESOLVER 5
 .Os
 .Sh NAME
@@ -127,6 +127,10 @@
 sets
 .Dv RES_DEBUG
 in _res.options.
+.It Sy usevc
+sets
+.Dv RES_USEVC
+to use TCP instead of UDP for queries.
 .It Sy ndots: Ns Ar n
 sets a threshold for the number of dots which must appear in a name given to
 .Fn res_query