diff --git a/lib/frames/attach_frame.js b/lib/frames/attach_frame.js
index <HASH>..<HASH> 100644
--- a/lib/frames/attach_frame.js
+++ b/lib/frames/attach_frame.js
@@ -239,7 +239,7 @@ AttachFrame.prototype._sourceAsPerformative = function(source) {
         distributionMode: source.distributionMode || null,
         filter: source.filter || {},
         defaultOutcome: source.defaultOutcome || null,
-        outcomes: source.outcomes || {},
+        outcomes: source.outcomes || null,
         capabilities: source.capabilities || null,
         encodeOrdering: ['address', 'durable', 'expiryPolicy', 'timeout', 'dynamic', 'dynamicNodeProperties',
             'distributionMode', 'filter', 'defaultOutcome', 'outcomes', 'capabilities']
Fix outcomes to default to null as opposed to empty map