diff --git a/Gemfile b/Gemfile
index 5991260..12d9b1d 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-source ENV['PROXY_RUBYGEMSORG'] || 'https://rubygems.org'
+source ENV.fetch('PROXY_RUBYGEMSORG', 'https://rubygems.org')
 
 # Install the `inspec` gem using `git` because versions after `4.22.22`
 # suppress diff output; this version fixes this for our uses.
diff --git a/ssf/files/default/Gemfile b/ssf/files/default/Gemfile
index c40d398..bfef20d 100644
--- a/ssf/files/default/Gemfile
+++ b/ssf/files/default/Gemfile
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-source ENV['PROXY_RUBYGEMSORG'] || 'https://rubygems.org'
+source ENV.fetch('PROXY_RUBYGEMSORG', 'https://rubygems.org')
 
 # Install the `inspec` gem using `git` because versions after `4.22.22`
 # suppress diff output; this version fixes this for our uses.