My bitcoin.conf file has the following lines:

rpcallowip=127.0.0.1
rpcallowip=192.168.*.*

But I'm getting this error:

Error: Invalid -rpcallowip subnet specification: 192.168.*. Valid are a single IP (e.g. 1.2.3.4), a network/netmask (e.g. 1.2.3.4/255.255.255.0) or a network/CIDR (e.g. 1.2.3.4/24).

How do I allow an IP range as I did before?