diff --git a/config/boot.rb b/config/boot.rb
index f3e36203a..6cde5319d 100644
--- a/config/boot.rb
+++ b/config/boot.rb
@@ -1,3 +1,8 @@
+unless ENV.key?('RAILS_ENV')
+  STDERR.puts 'ERROR: Missing RAILS_ENV environment variable, please set it to "production", "development", or "test".'
+  exit 1
+end
+
 ENV['BUNDLE_GEMFILE'] ||= File.expand_path('../Gemfile', __dir__)
 
 require 'bundler/setup' # Set up gems listed in the Gemfile.