1 files changed, 1 insertions, 1 deletions
diff --git a/lib/sourcemap.js b/lib/sourcemap.js
index 3714027e..0be16bfc 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);
 
     if (orig_map && Array.isArray(options.orig.sources)) {
-        options.orig.sources.forEach(function(source) {
+        orig_map._sources.toArray().forEach(function(source) {
             var sourceContent = orig_map.sourceContentFor(source, true);
             if (sourceContent) {
                 generator.setSourceContent(source, sourceContent);