diff --git a/lib/sourcemap.js b/lib/sourcemap.js
index 403b4f4d..6e98e547 100644
--- a/lib/sourcemap.js
+++ b/lib/sourcemap.js
@@ -60,7 +60,7 @@ function SourceMap(options) {
     var orig_map = options.orig && new MOZ_SourceMap.SourceMapConsumer(options.orig);
 
     // Copy across inline sourcesContent, if any
-    if (options.orig.sourcesContent) {
+    if (options.orig && options.orig.sourcesContent) {
         var len = options.orig.sourcesContent.length;
         for (var i = 0; i < len; i++) {
             generator.setSourceContent(options.orig.sources[i], options.orig.sourcesContent[i]);