Help setting up a slave

I get "xfer-in: transfer of 'foo.com/IN' from 9.9.9.9#53:
failed to connect: connection refused"

What can cause this? Can't be firewalls, I've disabled
all of that. Must be a misconfiguration.

9.9.9.9 = external address of master
9.9.9.8 = external address of slave
10.1.1.1 = internal address of slave

My slave says:
zone "foo.com" in {
type slave;
masters { 9.9.9.9; };
file "slave.foo.com";
};

My master says:
zone "foo.com" in {
type master;
file "db.foo.com";
allow-transfer { 10.1.1.1; 9.9.9.8; };
};

The log of my master shows:
queries: client 9.9.9.8#2693: query: foo.com IN SOA

db.foo.com includes:
@ IN SOA ns1.foo.com. (
hostmaster.foo.com. ; email
2005040100 ; serial
8h ; refresh
15m ; retry
30d ; expire
15m ) ; negative cache
IN NS ns1.foo.com.
IN NS ns2.foo.com.

There is no file slave.foo.com.