diff --git a/vendor/golang.org/x/sys/unix/syscall_dragonfly_amd64.go b/vendor/golang.org/x/sys/unix/syscall_dragonfly_amd64.go
index 9babb31..a6b4830 100644
--- a/vendor/golang.org/x/sys/unix/syscall_dragonfly_amd64.go
+++ b/vendor/golang.org/x/sys/unix/syscall_dragonfly_amd64.go
@@ -33,6 +33,10 @@
 	msghdr.Controllen = uint32(length)
 }
 
+func (msghdr *Msghdr) SetIovlen(length int) {
+	msghdr.Iovlen = int32(length)
+}
+
 func (cmsg *Cmsghdr) SetLen(length int) {
 	cmsg.Len = uint32(length)
 }