diff --git a/lib/package.js b/lib/package.js
index 18536694..9255ed4e 100644
--- a/lib/package.js
+++ b/lib/package.js
@@ -249,6 +249,8 @@
   var pkgConfigPromises = {};
   function createPackageNormalize(normalize, sync) {
     return function(name, parentName, isPlugin) {
+      isPlugin = isPlugin === true;
+      
       // apply contextual package map first
       if (parentName) {
         var parentPackage = getPackage.call(this, parentName) ||