diff --git a/packages/minimongo/observe.js b/packages/minimongo/observe.js
index 38bcb4514c..cc97ca73d0 100644
--- a/packages/minimongo/observe.js
+++ b/packages/minimongo/observe.js
@@ -157,6 +157,7 @@ LocalCollection._observeFromObserveChanges = function (cursor, observeCallbacks)
         var self = this;
         if (observeCallbacks.changed) {
           var oldDoc = self.docs.get(id);
+          oldDoc = EJSON.clone(oldDoc);
           var doc = EJSON.clone(oldDoc);
           LocalCollection._applyChanges(doc, fields);
           observeCallbacks.changed(transform(doc), transform(oldDoc));