Problem with ACL/address match lists

Hello everyone,

I am getting a little confused about address match lists.

Note: I am running BIND 9.1.1 and have no option to switch to a more
recent version as of now. So please don't just tell me not to use
9.1.1 any more - I would love to upgrade, but that is beyond my control...

I have a nameserver that will be running split-role with views.
I have defined an ACL like this:
###########################################
acl "myclients" {
10/8; 172.16/16; 192.168/16;
};
###########################################

Now I want to define my views like this:
###########################################
view "internal" {
match-clients { myclients; };
[...]
};

view "external" {
match-clients { !myclients; any; };
[...]
};
###########################################

However, when I try to make BIND reload its config, the following
line shows up in the logfile:
EZZ9212I /etc/tcpip/named.conf:116: undefined acl '!myclients' referenced

From the Bind9 ARM I see that '!' is supposed to work as a negator, just like in many
programming languages. A similar setup works on another machine running BIND 9.2 - is
this a problem with 9.1?

Thanks in advance,
Benjamin Walkenhorst