diff --git a/lib/loader.js b/lib/loader.js
index e3b28600..1a88770a 100644
--- a/lib/loader.js
+++ b/lib/loader.js
@@ -14,7 +14,7 @@ module.exports = function(content, map) {
 	var root = query.root;
 	var moduleMode = query.modules || query.module;
 
-	if(typeof map !== "string") {
+	if(map && typeof map !== "string") {
 		map = JSON.stringify(map);
 	}