diff --git a/src/lib/diff/tree-mutator-collection-binding.hpp b/src/lib/diff/tree-mutator-collection-binding.hpp
index 19c8d474a..03f7c5c79 100644
--- a/src/lib/diff/tree-mutator-collection-binding.hpp
+++ b/src/lib/diff/tree-mutator-collection-binding.hpp
@@ -403,13 +403,13 @@
         static bool
         default_contentMatch (GenNode const& spec, Elm const& elm)
           {
-            //return spec.matches(elm);
+            return spec.matches(elm);
           }
         
         static Elm
         default_construct_from_payload (GenNode const& spec)
           {
-            //return spec.data.get<Elm>();
+            return spec.data.get<Elm>();
           }
         
         static bool
diff --git a/tests/library/diff/tree-manipulation-binding-test.cpp b/tests/library/diff/tree-manipulation-binding-test.cpp
index e38f604ab..268b154ed 100644
--- a/tests/library/diff/tree-manipulation-binding-test.cpp
+++ b/tests/library/diff/tree-manipulation-binding-test.cpp
@@ -298,7 +298,19 @@ namespace test{
           // now set up a binding to these opaque private structures...
           auto mutator =
           TreeMutator::build()
-            .attach (collection(target));
+            .attach (collection(target)
+                       .constructFrom ([&](GenNode const& spec) -> Data
+                          {
+                            cout << "constructor invoked on "<<spec<<endl;
+                            return {spec.idi.getSym(), render(spec.data)};
+                          })
+                       .matchElement ([&](GenNode const& spec, Data const& elm)
+                          {
+                            cout << "match? "<<spec.idi.getSym()<<"=?="<<elm.key<<endl;
+                            return spec.idi.getSym() == elm.key;
+                          }
+                       )
+                       );
 
         }