diff --git a/index.js b/index.js
index 2d3b702..c0ebe2d 100644
--- a/index.js
+++ b/index.js
@@ -108,7 +108,7 @@ module.exports.assets = function (opts) {
 
                 // If any external streams were included, pipe all files to them first
                 streams.forEach(function (stream) {
-                    src.pipe(stream);
+                    src.pipe(stream());
                 });
 
                 // Add assets to the stream