diff --git a/src/net/udpsock.go b/src/net/udpsock.go
index 6d29a39edf..e30624dea5 100644
--- a/src/net/udpsock.go
+++ b/src/net/udpsock.go
@@ -164,6 +164,10 @@ func (c *UDPConn) ReadFrom(b []byte) (int, Addr, error) {
 }
 
 // ReadFromUDPAddrPort acts like ReadFrom but returns a netip.AddrPort.
+//
+// If c is bound to an unspecified address, the returned
+// netip.AddrPort's address might be an IPv4-mapped IPv6 address.
+// Use netip.Addr.Unmap to get the address without the IPv6 prefix.
 func (c *UDPConn) ReadFromUDPAddrPort(b []byte) (n int, addr netip.AddrPort, err error) {
 	if !c.ok() {
 		return 0, netip.AddrPort{}, syscall.EINVAL