diff --git a/script/boxen-git-credential b/script/boxen-git-credential
index d4a775e..a9b75a0 100755
--- a/script/boxen-git-credential
+++ b/script/boxen-git-credential
@@ -21,6 +21,11 @@ require "pathname"
 
 Dir.chdir Pathname.new(__FILE__).realpath + "../.."
 
+# Because we can be called from inside other Ruby processes, unset any
+# `BUNDLE_` environment variables.
+
+ENV.keys.select { |k| /^BUNDLE_/i }.each { |k| ENV.delete k }
+
 # Set up our local configuration, deps, and load path.
 
 load "config/basic.rb"