diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index 280231a..bf35252 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -1,5 +1,7 @@
 # This file is copied to spec/ when you run 'rails generate rspec:install'
-ENV["RAILS_ENV"] ||= 'test'
+# It's dangerous to use `||=' when setting ENV['RAILS_ENV'] here; see
+# https://github.com/rails/rails/issues/7175
+ENV["RAILS_ENV"] = 'test'
 require File.expand_path("../../config/environment", __FILE__)
 require 'rspec/rails'
 require 'email_spec'