diff --git a/src/duality/duality_rpfp.cpp b/src/duality/duality_rpfp.cpp
index e09278dd4..550f94f2d 100755
--- a/src/duality/duality_rpfp.cpp
+++ b/src/duality/duality_rpfp.cpp
@@ -2847,7 +2847,12 @@ namespace Duality {
   }
 
   void RPFP::InterpolateByCases(Node *root, Node *node){
+    timer_start("InterpolateByCases");
     bool axioms_added = false;
+    hash_set<ast> axioms_needed;
+    const std::vector<expr> &theory = ls->get_axioms();
+    for(unsigned i = 0; i < theory.size(); i++)
+      axioms_needed.insert(theory[i]);
     aux_solver.push();
     AddEdgeToSolver(node->Outgoing);
     node->Annotation.SetEmpty();
@@ -2869,7 +2874,17 @@ namespace Duality {
       check_result foo = Check(root);
       if(foo != unsat)
 	throw "should be unsat";
-      AddToProofCore(*core);
+
+      std::vector<expr> assumps, axioms_to_add;
+      slvr().get_proof().get_assumptions(assumps);
+      for(unsigned i = 0; i < assumps.size(); i++){
+	(*core).insert(assumps[i]);
+	if(axioms_needed.find(assumps[i]) != axioms_needed.end()){
+	  axioms_to_add.push_back(assumps[i]);
+	  axioms_needed.erase(assumps[i]);
+	}
+      }
+      // AddToProofCore(*core);
       Transformer old_annot = node->Annotation;
       SolveSingleNode(root,node);
 
@@ -2882,6 +2897,9 @@ namespace Duality {
 	node->Annotation.Formula = node->Annotation.Formula.simplify();
       }
 
+      for(unsigned i = 0; i < axioms_to_add.size(); i++)
+	aux_solver.add(axioms_to_add[i]);
+      
       if(node->Annotation.IsEmpty()){
 	if(!axioms_added){
 	  // add the axioms in the off chance they are useful
@@ -2906,6 +2924,7 @@ namespace Duality {
       delete proof_core; // shouldn't happen
     proof_core = core;
     aux_solver.pop(1);
+    timer_stop("InterpolateByCases");
   }
 
   void RPFP::Generalize(Node *root, Node *node){
diff --git a/src/duality/duality_wrapper.cpp b/src/duality/duality_wrapper.cpp
index cf2c803cb..345fef562 100755
--- a/src/duality/duality_wrapper.cpp
+++ b/src/duality/duality_wrapper.cpp
@@ -43,7 +43,8 @@ namespace Duality {
     if(models)
       p.set_bool("model", true); 
     p.set_bool("unsat_core", true); 
-    p.set_bool("mbqi",true);
+    bool mbqi = c.get_config().get().get_bool("mbqi",true);
+    p.set_bool("mbqi",mbqi); // just to test
     p.set_str("mbqi.id","itp"); // use mbqi for quantifiers in interpolants
     p.set_uint("mbqi.max_iterations",1); // use mbqi for quantifiers in interpolants
     if(true || extensional)
diff --git a/src/duality/duality_wrapper.h b/src/duality/duality_wrapper.h
index 2b0045023..febc3f1f1 100755
--- a/src/duality/duality_wrapper.h
+++ b/src/duality/duality_wrapper.h
@@ -182,6 +182,7 @@ namespace Duality {
       void set(char const * param, char const * value) { m_config.set(param,value); }
       void set(char const * param, bool value) { m_config.set(param,value); }
       void set(char const * param, int value) { m_config.set(param,value); }
+      config &get_config() {return m_config;}
 
       symbol str_symbol(char const * s);
       symbol int_symbol(int n);
diff --git a/src/muz/base/fixedpoint_params.pyg b/src/muz/base/fixedpoint_params.pyg
index e09e1307b..5eec77f39 100644
--- a/src/muz/base/fixedpoint_params.pyg
+++ b/src/muz/base/fixedpoint_params.pyg
@@ -74,6 +74,7 @@ def_module_params('fixedpoint',
 			  ('stratified_inlining', BOOL, False, 'DUALITY: Use stratified inlining'),
 			  ('recursion_bound', UINT, UINT_MAX, 'DUALITY: Recursion bound for stratified inlining'),
 			  ('profile', BOOL, False, 'DUALITY: profile run time'),
+			  ('mbqi', BOOL, True, 'DUALITY: use model-based quantifier instantion'),
                           ('dump_aig', SYMBOL, '', 'Dump clauses in AIG text format (AAG) to the given file name'),
                           ))
 
diff --git a/src/muz/duality/duality_dl_interface.cpp b/src/muz/duality/duality_dl_interface.cpp
index 248aca163..e7c7976f6 100755
--- a/src/muz/duality/duality_dl_interface.cpp
+++ b/src/muz/duality/duality_dl_interface.cpp
@@ -141,6 +141,7 @@ lbool dl_interface::query(::expr * query) {
 
   // make a new problem and solver
   _d = alloc(duality_data,m_ctx.get_manager());
+  _d->ctx.set("mbqi",m_ctx.get_params().mbqi());
   _d->ls = alloc(RPFP::iZ3LogicSolver,_d->ctx);
   _d->rpfp = alloc(RPFP,_d->ls);