diff --git a/src/installer.js b/src/installer.js
index f9d0897de..bc26dc153 100644
--- a/src/installer.js
+++ b/src/installer.js
@@ -76,7 +76,7 @@ function retire(args, callback) {
 }
 
 function ensureVersion(args, callback) {
-    assert.strictEqual(typeof args, 'Object');
+    assert.strictEqual(typeof args, 'object');
     assert.strictEqual(typeof callback, 'function');
 
     if (args.sourceTarballUrl) return callback(null, args.sourceTarballUrl);