CONTRIBUTING.md in bunny-2.11.0 vs CONTRIBUTING.md in bunny-2.12.0.rc1

@@ -88,10 +88,10 @@
 Version >= 1.6.0+ is required for compose version 2 syntax.
 
 After those have been installed (and the `docker-compose` command is available on your command line path), run
 
 ```
-docker-compose up
+docker-compose build && docker-compose up
 ```
 
 The first time you do this, it will take some time, since it has to download everything it needs
 to build the Docker image.