--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -397,6 +397,7 @@ struct pg_conn
    int         nconnhost;      /* # of hosts named in conn string */
    int         whichhost;      /* host we're currently trying/connected to */
    pg_conn_host *connhost;     /* details about each named host */
+   int         read_write_host_index; /* index for first read-write host in connhost */
 
    /* Connection data */
    pgsocket    sock;           /* FD for socket, PGINVALID_SOCKET if