diff --git a/src/lib/diff/tree-diff-application.hpp b/src/lib/diff/tree-diff-application.hpp
index 2112ee5c8..2e8794471 100644
--- a/src/lib/diff/tree-diff-application.hpp
+++ b/src/lib/diff/tree-diff-application.hpp
@@ -155,12 +155,13 @@ namespace diff{
       Scopes scopes_;
       
       
-      void
+      TreeMutator*
       buildMutator (DiffMutable& targetBinding)
         {
           scopes_.clear();
           TreeMutator::Handle buffHandle = scopes_.openScope();
           targetBinding.buildMutator (buffHandle);
+          return buffHandle.get();
         }
       
     public:
diff --git a/src/lib/diff/tree-diff-mutator-binding.cpp b/src/lib/diff/tree-diff-mutator-binding.cpp
index 305476f17..a92461a20 100644
--- a/src/lib/diff/tree-diff-mutator-binding.cpp
+++ b/src/lib/diff/tree-diff-mutator-binding.cpp
@@ -267,7 +267,11 @@ namespace diff{
   void
   TreeDiffMutatorBinding::__expect_end_of_scope (GenNode::ID const& idi)
   {
-    
+    if (not treeMutator_->completeScope())
+      throw error::State(_Fmt("Diff application floundered in nested scope %s; "
+                              "unexpected extra elements found when diff "
+                              "should have settled everything.") % idi.getSym()
+                        , LUMIERA_ERROR_DIFF_CONFLICT);
   }
   
   void
@@ -349,24 +353,22 @@ namespace diff{
   void
   TreeDiffMutatorBinding::mut (GenNode const& n)
   {
-    open_subScope (n);
+    TreeMutator::Handle buffHandle = scopeManger_->openScope();
+    if (not treeMutator_->mutateChild(n, buffHandle))
+      __failMismatch (n, "enter nested scope");
     
-#if false /////////////////////////////////////////////////////////////////////////////////////////////////////////////UNIMPLEMENTED :: TICKET #992
-    Rec const& childRecord = child.data.get<Rec>();
-    TRACE (diff, "tree-diff: ENTER scope %s", cStr(childRecord));
-#endif    /////////////////////////////////////////////////////////////////////////////////////////////////////////////UNIMPLEMENTED :: TICKET #992
+    TRACE (diff, "tree-diff: ENTER scope %s", cStr(n.idi));
+    treeMutator_ = buffHandle.get();
   }
   
   /** finish and leave child object scope, return to parent */
   void
   TreeDiffMutatorBinding::emu (GenNode const& n)
   {
-#if false /////////////////////////////////////////////////////////////////////////////////////////////////////////////UNIMPLEMENTED :: TICKET #992
-    TRACE (diff, "tree-diff: LEAVE scope %s", cStr(describeScope()));
-#endif    /////////////////////////////////////////////////////////////////////////////////////////////////////////////UNIMPLEMENTED :: TICKET #992
+    TRACE (diff, "tree-diff: LEAVE scope %s", cStr(n.idi));
     
     __expect_end_of_scope (n.idi);
-    close_subScope();
+    treeMutator_ = &scopeManger_->closeScope();
     __expect_valid_parent_scope (n.idi);
   }
   
diff --git a/src/lib/diff/tree-diff-mutator-binding.hpp b/src/lib/diff/tree-diff-mutator-binding.hpp
index e581a2b05..e07c5cc67 100644
--- a/src/lib/diff/tree-diff-mutator-binding.hpp
+++ b/src/lib/diff/tree-diff-mutator-binding.hpp
@@ -289,14 +289,6 @@ namespace diff{
       
       
       
-      /* == Forwarding: mutation primitives == */
-      
-      bool matchSrc (GenNode const& n);
-      void assignElm (GenNode const& n);
-      void open_subScope (GenNode const& n);
-      void close_subScope();
-      
-      
       
       /* == Implementation of the list diff application primitives == */
       
diff --git a/src/lib/diff/tree-mutator.hpp b/src/lib/diff/tree-mutator.hpp
index 2803c2417..8546e70ce 100644
--- a/src/lib/diff/tree-mutator.hpp
+++ b/src/lib/diff/tree-mutator.hpp
@@ -154,6 +154,14 @@ namespace lib {
         {
           return sizeof(SUB) <= maxSiz_;
         }
+      
+      BA*
+      get()  const
+        {
+          ENSURE (buffer_);
+          BA& bufferContent = **static_cast<InPlaceBuffer<BA>*> (buffer_);
+          return &bufferContent;
+        }
     };
   /////////////////////////////TODO move over into opaque-holder.hpp
 namespace diff{
@@ -286,7 +294,7 @@ namespace diff{
        *  and build a suitable sub-mutator for this element
        *  into the provided target buffer
        * @throw error::Fatal when buffer is insufficient
-       * @return false when unable to locate the target */
+       * @return `false` when unable to locate the target */
       virtual bool
       mutateChild (GenNode const&, Handle)
         {
diff --git a/tests/library/diff/diff-virtualised-application-test.cpp b/tests/library/diff/diff-virtualised-application-test.cpp
index 02ce37a3c..d29f16a64 100644
--- a/tests/library/diff/diff-virtualised-application-test.cpp
+++ b/tests/library/diff/diff-virtualised-application-test.cpp
@@ -79,7 +79,7 @@ namespace test{
      */
     class Opaque
       {
-        idi::EntryID<Opaque> key_;
+        idi::BareEntryID key_;
         string type_ = Rec::TYPE_NIL;
         
         int  alpha_   = -1;
@@ -92,11 +92,13 @@ namespace test{
         vector<string> nestedData_;
         
       public:
-        Opaque() { }
+        Opaque()
+          : key_(idi::EntryID<Opaque>())
+          { }
         
         explicit
         Opaque (string keyID)
-          : key_(keyID)
+          : key_(idi::EntryID<Opaque>(keyID))
           { }
         
         explicit
@@ -132,14 +134,15 @@ namespace test{
         
         operator string()  const
           {
-            return _Fmt{"%s (α:%d β:%s γ:%7.5f δ:%s\n......|nested:%s\n......|data:%s\n      )"}
+            return _Fmt{"%s__(α:%d β:%s γ:%7.5f δ:%s\n......|nested:%s\n......|data:%s\n      )__END_%s"}
                        % identity()
                        % alpha_
                        % beta_
                        % gamma_
                        % delta_
-                       % join (nestedObj_, "\n........|")
+                       % join (nestedObj_, "\n......|")
                        % join (nestedData_)
+                       % identity()
                        ;
           }
         
@@ -347,7 +350,7 @@ namespace test{
           // TODO verify results
           cout << "after...II"<<endl << subject<<endl;
           
-          // Part II : apply child mutations
+          // Part III : apply child mutations
           application.consume(mutationDiff());
           //
           // TODO verify results