ERROR: Use of -r/--rules-file and -g/--rules-generate only allowed in attack mode 0.

[lcrom]

Running hashcat 3.6.0 (althought hashcat --version shows 'pull/1273/head'). I'm getting this error:

Use of -r/--rules-file and -g/--rules-generate only allowed in attack mode 0.

This is the command I'm using:

hashcat -m 0 -a 1 ./hashes-long.txt ./rockyou.txt -r /usr/share/hashcat/rules/combinator.rule

I don't know why it thinks I'm using '-g'. I'm new to hashcat, so maybe I'm missing a step? Shouldn't this work?