diff --git a/build/output/browser/postal.js b/build/output/browser/postal.js
index 59b0469..dad71b1 100644
--- a/build/output/browser/postal.js
+++ b/build/output/browser/postal.js
@@ -28,8 +28,8 @@ var DEFAULT_EXCHANGE = "/",
     NO_OP = function() { };
 
 var defaultConfiguration = {
-    exchange: exchange || DEFAULT_EXCHANGE,
-    topic: topic || "",
+    exchange: DEFAULT_EXCHANGE,
+    topic: "",
     callback: NO_OP,
     priority: DEFAULT_PRIORITY,
     constraints: [],
@@ -40,7 +40,7 @@ var defaultConfiguration = {
 };
 
 var ChannelDefinition = function(exchange, topic) {
-    this.configuration = defaultConfiguration;
+    this.configuration = _.extend(defaultConfiguration, { exchange: exchange, topic: topic });
 } ;
 
 ChannelDefinition.prototype = {
diff --git a/build/output/nodejs/postal.js b/build/output/nodejs/postal.js
index 9a427c2..7e6dc0e 100644
--- a/build/output/nodejs/postal.js
+++ b/build/output/nodejs/postal.js
@@ -26,8 +26,8 @@ var DEFAULT_EXCHANGE = "/",
     NO_OP = function() { };
 
 var defaultConfiguration = {
-    exchange: exchange || DEFAULT_EXCHANGE,
-    topic: topic || "",
+    exchange: DEFAULT_EXCHANGE,
+    topic: "",
     callback: NO_OP,
     priority: DEFAULT_PRIORITY,
     constraints: [],
@@ -38,7 +38,7 @@ var defaultConfiguration = {
 };
 
 var ChannelDefinition = function(exchange, topic) {
-    this.configuration = defaultConfiguration;
+    this.configuration = _.extend(defaultConfiguration, { exchange: exchange, topic: topic });
 } ;
 
 ChannelDefinition.prototype = {