diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 6ed3205c..c975a937 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -29,6 +29,7 @@ Create and setup a test database:
 export PGDATABASE=pgx_test
 createdb
 psql -c 'create extension hstore;'
+psql -c 'create extension ltree;'
 psql -c 'create domain uint64 as numeric(20,0);'
 ```