diff --git a/src/resty/dns/balancer/base.lua b/src/resty/dns/balancer/base.lua
index 1e8ea30..1af784b 100644
--- a/src/resty/dns/balancer/base.lua
+++ b/src/resty/dns/balancer/base.lua
@@ -1275,11 +1275,18 @@ end
 --
 -- Signature of the callback is for address adding/removing:
 --
---   `function(balancer, "added"/"removed", address, ip, port, hostname)`
---
--- where `ip` might also
--- be a hostname if the DNS resolution returns another name (usually in
--- SRV records).
+--   `function(balancer, "added"/"removed", address, ip, port, hostname, hostheader)`
+--
+-- - `address` is the address object added
+-- - `ip` is the IP address for this object, but might also be a hostname if
+--   the DNS resolution returns another name (usually in SRV records)
+-- - `port` is the port to use
+-- - `hostname` is the hostname for which the address was added to the balancer
+--   with `addHost` (resolving that name caused the creation of this address)
+-- - `hostheader` is the hostheader to be used. This can have 3 values; 1) `nil` if the
+--   `hostname` added was an ip-address to begin with, 2) it will be equal to the
+--   name in `ip` if there is a named SRV entry, and `useSRVname == true`, 3) otherwise
+--   it will be equal to `hostname`
 --
 -- For health updates the signature is:
 --