diff --git a/lib/configure.js b/lib/configure.js
index 7992b658a4..2fe760c775 100644
--- a/lib/configure.js
+++ b/lib/configure.js
@@ -96,7 +96,7 @@ function configure (gyp, argv, callback) {
 
     log.verbose('build/' + configFilename, 'creating config file')
 
-    var config = Object.assign({}, process.config)
+    var config = process.config ? JSON.parse(JSON.stringify(process.config)) : {}
     var defaults = config.target_defaults
     var variables = config.variables