gistfile1.diff

diff --git a/src/compojure/http/middleware.clj b/src/compojure/http/middleware.clj
index eb0c276..b79e544 100644
--- a/src/compojure/http/middleware.clj
+++ b/src/compojure/http/middleware.clj
@@ -32,9 +32,9 @@
    existing headers."
   [handler headers]
   (fn [request]
-    (let [response (handler request)
-          merged-headers (merge (:headers response) headers)]
-      (assoc response :headers merged-headers))))
+    (if-let [response (handler request)]
+      (assoc response :headers 
+	     (merge (:headers response) headers)))))
 
 (defn with-cache-control
    "Middleware to set the Cache-Control http header. Map entries with boolean