diff --git a/man5/resolv.conf.5 b/man5/resolv.conf.5
index 8f1b2bc79..d5318f3d8 100644
--- a/man5/resolv.conf.5
+++ b/man5/resolv.conf.5
@@ -255,6 +255,10 @@ and IPv4 requests sequentially (at the cost of some slowdown of the
 resolving process).
 .TP
 .BR single-request-reopen " (since glibc 2.9)"
+sets
+.BR RES_SNGLKUPREOP
+in
+.IR _res.options .
 The resolver uses the same socket for the A and AAAA requests.
 Some hardware mistakenly sends back only one reply.
 When that happens the client system will sit and wait for the second reply.