diff --git a/doc/src/sgml/protocol.sgml b/doc/src/sgml/protocol.sgml
index a746c967053..2212ed677ec 100644
--- a/doc/src/sgml/protocol.sgml
+++ b/doc/src/sgml/protocol.sgml
@@ -5317,8 +5317,10 @@ psql "dbname=postgres replication=database" -c "IDENTIFY_SYSTEM;"
        <term>Byte1('v')</term>
        <listitem>
         <para>
-         Identifies the message as a protocol version negotiation
-         message.
+         Identifies the message as a protocol version negotiation message.
+         The server sends this message when the client requests a major protocol version
+         that the server supports and a newer minor protocol version than the server supports,
+         or when the client includes protocol options that the server does not recognize.
         </para>
        </listitem>
       </varlistentry>
@@ -5336,8 +5338,12 @@ psql "dbname=postgres replication=database" -c "IDENTIFY_SYSTEM;"
        <term>Int32</term>
        <listitem>
         <para>
-         Newest minor protocol version supported by the server
-         for the major protocol version requested by the client.
+         The latest protocol version supported by the server if the client
+         requests a newer protocol version than the server supports.
+         The protocol version requested by the client, otherwise.
+         The most significant 16 bits are the major version number, and the least
+         significant 16 bits are the minor version number. This will be the version
+         of the protocol which will be used for the duration of the connection.
         </para>
        </listitem>
       </varlistentry>