Build Error on ubuntu 18.04 with Racket 6.11

[braddockcg]

I get an error on build or when I try to run with Racket v6.11 on Ubuntu 18.04:
compiler/ast.rkt:4:22: collection not found

The specific error from make is:

git clone https://github.com/stamourv/picobit.git
sudo apt install racket gawk
make
[...]
raco make compiler/picobit.rkt
compiler/ast.rkt:4:22: collection not found
  for module path: unstable/match
  collection: "unstable"
  in collection directories:
   /home/braddock/.racket/6.11/collects
   /usr/share/racket/collects
   ... [159 additional linked and package directories]
  compilation context...:
   /home/braddock/expire/repo/picobit/compiler/ast.rkt
   /home/braddock/expire/repo/picobit/compiler/picobit.rkt
  context...:
   show-collection-err
   standard-module-name-resolver
   /usr/share/racket/collects/compiler/cm.rkt:363:0: compile-zo*
   /usr/share/racket/collects/compiler/cm.rkt:572:26
   /usr/share/racket/collects/compiler/cm.rkt:564:42
   /usr/share/racket/collects/compiler/cm.rkt:635:0: compile-root
   /usr/share/racket/collects/compiler/cm.rkt:782:4: compilation-manager-load-handler
   standard-module-name-resolver
   /usr/share/racket/collects/compiler/cm.rkt:363:0: compile-zo*
   /usr/share/racket/collects/compiler/cm.rkt:572:26
   /usr/share/racket/collects/compiler/cm.rkt:564:42
   /usr/share/racket/collects/compiler/cm.rkt:635:0: compile-root
   /usr/share/racket/collects/compiler/cm.rkt:737:4
   /usr/share/racket/pkgs/compiler-lib/compiler/commands/make.rkt:81:8: for-loop
   /usr/share/racket/pkgs/compiler-lib/compiler/commands/make.rkt: [running body]
   /usr/share/racket/collects/raco/raco.rkt: [running body]
   ...
Makefile:7: recipe for target 'compiler' failed
make: *** [compiler] Error 1

$ racket --version
Welcome to Racket v6.11.

[braddockcg]

Same error confirmed when using Racket v7.2 (Jan 2019) installed via PPA.

[stamourv]

I haven't looked at this in forever, but running raco pkg install unstable should fix it.

[braddockcg]

Thank you, that fixed it and picobit now builds and runs.
Sorry for the newbie question, I've never used Racket.