I'm doing a box on Hackthebox and I'm running into a problem when I try to use gobuster. When I run:

gobuster -u http://TARGET_IP:PORT -w /usr/share/wordlists/dirbuster/directory-list-lowercase-2.3-medium.txt -t 100

I get this output:
Error: unknown shorthand flag: 'u' in -u

I tried removing and reinstalling the program with apt-get remove, and run apt-get update and apt-get upgrade, but I can't figure out how to fix this. Anyone have any insight?