diff --git a/doc/api/dgram.md b/doc/api/dgram.md
index 7a09c9385a82a6..df479a8e31df60 100644
--- a/doc/api/dgram.md
+++ b/doc/api/dgram.md
@@ -78,10 +78,11 @@ added: v0.6.9
 * `multicastAddress` {String}
 * `multicastInterface` {String}, Optional
 
-Tells the kernel to join a multicast group at the given `multicastAddress`
-using the `IP_ADD_MEMBERSHIP` socket option. If the `multicastInterface`
-argument is not specified, the operating system will try to add membership to
-all valid networking interfaces.
+Tells the kernel to join a multicast group at the given `multicastAddress` and
+`multicastInterface` using the `IP_ADD_MEMBERSHIP` socket option. If the
+`multicastInterface` argument is not specified, the operating system will choose
+one interface and will add membership to it. To add membership to every
+available interface, call `addMembership` multiple times, once per interface.
 
 ### socket.address()