diff --git a/src/filters/nested.js b/src/filters/nested.js
index 933cf740..fde73aac 100644
--- a/src/filters/nested.js
+++ b/src/filters/nested.js
@@ -50,9 +50,11 @@ var patchFilter = function nestedPatchFilter(context) {
     if (!context.nested) { return; }
     if (context.delta._t) { return; }
     var name, child;
-    for (name in context.delta) {
-        child = new PatchContext(context.left[name], context.delta[name]);
-        context.push(child, name);
+    if(context.left) {
+        for (name in context.delta) {
+            child = new PatchContext(context.left[name], context.delta[name]);
+            context.push(child, name);
+        }
     }
     context.exit();
 };
@@ -106,4 +108,4 @@ exports.objectsDiffFilter = objectsDiffFilter;
 exports.patchFilter = patchFilter;
 exports.collectChildrenPatchFilter = collectChildrenPatchFilter;
 exports.reverseFilter = reverseFilter;
-exports.collectChildrenReverseFilter = collectChildrenReverseFilter;
\ No newline at end of file
+exports.collectChildrenReverseFilter = collectChildrenReverseFilter;