diff --git a/README.md b/README.md
index ba1f72c1..0ceaaa77 100644
--- a/README.md
+++ b/README.md
@@ -17,8 +17,8 @@ If the prerequisites are met you can use the PGXN Client to download, build, and
 
 ```
 $ pgxn install h3
-$ pgxn load -d mydb h3
-$ psql -d mydb
+$ pgxn load h3
+$ psql
 =# SELECT h3_geo_to_h3(POINT('37.3615593,-122.0553238'), 5);
   h3_geo_to_h3   
 -----------------
diff --git a/docker/build.Dockerfile b/docker/build.Dockerfile
index fc51f27b..b72d94e2 100644
--- a/docker/build.Dockerfile
+++ b/docker/build.Dockerfile
@@ -1,4 +1,4 @@
-ARG UBUNTU
+ARG UBUNTU=xenial
 FROM h3-pg:base-${UBUNTU}
 ARG UBUNTU
 ARG POSTGRESQL
diff --git a/docker/pgxn.Dockerfile b/docker/pgxn.Dockerfile
index 27599813..d659d7f0 100644
--- a/docker/pgxn.Dockerfile
+++ b/docker/pgxn.Dockerfile
@@ -1,4 +1,4 @@
-ARG UBUNTU
+ARG UBUNTU=xenial
 FROM h3-pg:base-${UBUNTU}
 ARG UBUNTU
 ARG POSTGRESQL