diff --git a/src/ast/datatype_decl_plugin.cpp b/src/ast/datatype_decl_plugin.cpp
index ee3271b9b..5b29ec20b 100644
--- a/src/ast/datatype_decl_plugin.cpp
+++ b/src/ast/datatype_decl_plugin.cpp
@@ -521,6 +521,20 @@ func_decl * datatype_decl_plugin::mk_func_decl(decl_kind k, unsigned num_paramet
             return m_manager->mk_func_decl(a_name, arity, domain, a_type, info);
         }
         break;
+    case OP_DT_UPDATE_FIELD:
+        if (num_parameters != 2 || arity != 2 || domain[0] != datatype) { 
+            m_manager->raise_exception("invalid parameters for datatype field update");
+            return 0;
+        }
+        else {
+            symbol con_name = parameters[0].get_symbol();
+            symbol acc_name = parameters[1].get_symbol();
+            func_decl_info info(m_family_id, k, num_parameters, parameters);
+            info.m_private_parameters = true;
+            SASSERT(info.private_parameters());
+            return m_manager->mk_func_decl(symbol("update_field"), arity, domain, datatype, info);
+        }
+        
     default:
         m_manager->raise_exception("invalid datatype operator kind");
         return 0;
@@ -672,6 +686,16 @@ bool datatype_decl_plugin::is_value(app * e) const {
     return true;
 }
 
+void datatype_decl_plugin::get_op_names(svector<builtin_name> & op_names, symbol const & logic) {
+#if 0
+    // disabled
+    if (logic == symbol::null) {
+        op_names.push_back(builtin_name("update_field", OP_DT_UPDATE_FIELD));
+    }
+#endif
+}
+
+
 datatype_util::datatype_util(ast_manager & m):
     m_manager(m),
     m_family_id(m.mk_family_id("datatype")),
@@ -919,9 +943,9 @@ void datatype_util::display_datatype(sort *s0, std::ostream& strm) {
     todo.push_back(s0);
     mark.mark(s0, true);
     while (!todo.empty()) {
-		sort* s = todo.back();
+        sort* s = todo.back();
         todo.pop_back();
-		strm << s->get_name() << " =\n";
+        strm << s->get_name() << " =\n";
 
         ptr_vector<func_decl> const * cnstrs = get_datatype_constructors(s);
         for (unsigned i = 0; i < cnstrs->size(); ++i) {
@@ -931,14 +955,14 @@ void datatype_util::display_datatype(sort *s0, std::ostream& strm) {
             ptr_vector<func_decl> const * accs = get_constructor_accessors(cns);
             for (unsigned j = 0; j < accs->size(); ++j) {
                 func_decl* acc = (*accs)[j];
-				sort* s1 = acc->get_range();
+                sort* s1 = acc->get_range();
                 strm << "(" << acc->get_name() << ": " << s1->get_name() << ") "; 
                 if (is_datatype(s1) && are_siblings(s1, s0) && !mark.is_marked(s1)) {
                         mark.mark(s1, true);
                         todo.push_back(s1);
                 }          
             }
-			strm << "\n";
+            strm << "\n";
         }
     }
 
diff --git a/src/ast/datatype_decl_plugin.h b/src/ast/datatype_decl_plugin.h
index 96b678fb2..af7c689bc 100644
--- a/src/ast/datatype_decl_plugin.h
+++ b/src/ast/datatype_decl_plugin.h
@@ -32,6 +32,7 @@ enum datatype_op_kind {
     OP_DT_CONSTRUCTOR,
     OP_DT_RECOGNISER,
     OP_DT_ACCESSOR,
+    OP_DT_UPDATE_FIELD,
     LAST_DT_OP
 };
 
@@ -149,6 +150,8 @@ public:
 
     virtual bool is_unique_value(app * e) const { return is_value(e); }
 
+    virtual void get_op_names(svector<builtin_name> & op_names, symbol const & logic);
+
 private:
     bool is_value_visit(expr * arg, ptr_buffer<app> & todo) const;
 };
diff --git a/src/smt/theory_pb.cpp b/src/smt/theory_pb.cpp
index b8a5e7bd1..1eff86db4 100644
--- a/src/smt/theory_pb.cpp
+++ b/src/smt/theory_pb.cpp
@@ -321,7 +321,7 @@ namespace smt {
                     m_simplex.get_upper(v, last_bound);
                     if (m_mpq_inf_mgr.gt(bound, last_bound)) {
                         literal lit = m_explain_upper.get(v, null_literal);
-                        get_context().mk_clause(~lit, ~explain, 0);
+                        get_context().mk_clause(~lit, ~explain, justify(~lit, ~explain));
                         return false;
                     }
                 }
@@ -341,7 +341,7 @@ namespace smt {
                     m_simplex.get_lower(v, last_bound);
                     if (m_mpq_inf_mgr.gt(last_bound, bound)) {
                         literal lit = m_explain_lower.get(v, null_literal);
-                        get_context().mk_clause(~lit, ~explain, 0);
+                        get_context().mk_clause(~lit, ~explain, justify(~lit, ~explain));
                         return false;
                     }
                 }
@@ -358,6 +358,7 @@ namespace smt {
     };
 
     bool theory_pb::check_feasible() {
+        context& ctx = get_context();
         lbool is_sat = m_simplex.make_feasible();
         if (l_false != is_sat) {
             return true;
@@ -400,7 +401,10 @@ namespace smt {
 
         m_stats.m_num_conflicts++;
         justification* js = 0;
-        get_context().mk_clause(lits.size(), lits.c_ptr(), js, CLS_AUX_LEMMA, 0);
+        if (proofs_enabled()) {                                         
+            js = alloc(theory_lemma_justification, get_id(), ctx, lits.size(), lits.c_ptr());
+        }
+        ctx.mk_clause(lits.size(), lits.c_ptr(), js, CLS_AUX_LEMMA, 0);
 
         return false;
     }
@@ -1143,12 +1147,14 @@ namespace smt {
     struct theory_pb::psort_expr {
         context&     ctx;
         ast_manager& m;
+        theory_pb&   th;
         typedef smt::literal literal;
         typedef smt::literal_vector literal_vector;
       
-        psort_expr(context& c):
+        psort_expr(context& c, theory_pb& th):
             ctx(c), 
-            m(c.get_manager()) {}
+            m(c.get_manager()),
+            th(th) {}
 
         literal fresh() {
             app_ref y(m);
@@ -1180,7 +1186,7 @@ namespace smt {
 
         void mk_clause(unsigned n, literal const* ls) {
             literal_vector tmp(n, ls);
-            ctx.mk_clause(n, tmp.c_ptr(), 0, CLS_AUX, 0);
+            ctx.mk_clause(n, tmp.c_ptr(), th.justify(tmp), CLS_AUX, 0);
         }
 
         literal mk_false() { return false_literal; }
@@ -1192,7 +1198,9 @@ namespace smt {
 
     // for testing
     literal theory_pb::assert_ge(context& ctx, unsigned k, unsigned n, literal const* xs) {
-        psort_expr ps(ctx);
+        theory_pb_params p;
+        theory_pb th(ctx.get_manager(), p);
+        psort_expr ps(ctx, th);
         psort_nw<psort_expr> sort(ps);
         return sort.ge(false, k, n, xs);
     }
@@ -1249,21 +1257,21 @@ namespace smt {
         }
         if (ctx.get_assignment(thl) == l_true  && 
             ctx.get_assign_level(thl) == ctx.get_base_level()) {
-            psort_expr ps(ctx);
+            psort_expr ps(ctx, *this);
             psort_nw<psort_expr> sortnw(ps);
             sortnw.m_stats.reset();
             at_least_k = sortnw.ge(false, k, in.size(), in.c_ptr());
-            ctx.mk_clause(~thl, at_least_k, 0);
+            ctx.mk_clause(~thl, at_least_k, justify(~thl, at_least_k));
             m_stats.m_num_compiled_vars += sortnw.m_stats.m_num_compiled_vars;
             m_stats.m_num_compiled_clauses += sortnw.m_stats.m_num_compiled_clauses;
         }
         else {
-            psort_expr ps(ctx);
+            psort_expr ps(ctx, *this);
             psort_nw<psort_expr> sortnw(ps);
             sortnw.m_stats.reset();
             literal at_least_k = sortnw.ge(true, k, in.size(), in.c_ptr());
-            ctx.mk_clause(~thl, at_least_k, 0);
-            ctx.mk_clause(~at_least_k, thl, 0);
+            ctx.mk_clause(~thl, at_least_k, justify(~thl, at_least_k));
+            ctx.mk_clause(~at_least_k, thl, justify(thl, ~at_least_k));
             m_stats.m_num_compiled_vars += sortnw.m_stats.m_num_compiled_vars;
             m_stats.m_num_compiled_clauses += sortnw.m_stats.m_num_compiled_clauses;
         }
@@ -1432,7 +1440,9 @@ namespace smt {
         if (m_conflict_frequency == 0 || (m_conflict_frequency -1 == (c.m_num_propagations % m_conflict_frequency))) {
             resolve_conflict(c);
         }
-
+        if (proofs_enabled()) {                                         
+            js = alloc(theory_lemma_justification, get_id(), ctx, lits.size(), lits.c_ptr());
+        }
         ctx.mk_clause(lits.size(), lits.c_ptr(), js, CLS_AUX_LEMMA, 0);
     }
 
@@ -1739,7 +1749,7 @@ namespace smt {
             for (unsigned i = 0; i < m_ineq_literals.size(); ++i) {
                 m_ineq_literals[i].neg();
             }
-            ctx.mk_clause(m_ineq_literals.size(), m_ineq_literals.c_ptr(), 0, CLS_AUX_LEMMA, 0);
+            ctx.mk_clause(m_ineq_literals.size(), m_ineq_literals.c_ptr(), justify(m_ineq_literals), CLS_AUX_LEMMA, 0);
             break;
         default: {
             app_ref tmp = m_lemma.to_expr(false, ctx, get_manager());
@@ -1757,6 +1767,22 @@ namespace smt {
         return typeid(smt::justification_proof_wrapper) == typeid(j);
     }
 
+    justification* theory_pb::justify(literal l1, literal l2) {
+        literal lits[2] = { l1, l2 };
+        justification* js = 0;
+        if (proofs_enabled()) {                                         
+            js = alloc(theory_axiom_justification, get_id(), get_context().get_region(), 2, lits);
+        }
+        return js;
+    }
+
+    justification* theory_pb::justify(literal_vector const& lits) {
+        justification* js = 0;
+        if (proofs_enabled()) {                                         
+            js = alloc(theory_lemma_justification, get_id(), get_context(), lits.size(), lits.c_ptr());
+        }
+        return js;        
+    }
 
     void theory_pb::hoist_maximal_values() {
         for (unsigned i = 0; i < m_lemma.size(); ++i) {
diff --git a/src/smt/theory_pb.h b/src/smt/theory_pb.h
index b7922fbd0..b9fddba38 100644
--- a/src/smt/theory_pb.h
+++ b/src/smt/theory_pb.h
@@ -289,6 +289,11 @@ namespace smt {
         void validate_final_check(ineq& c);
         void validate_assign(ineq const& c, literal_vector const& lits, literal l) const;
         void validate_watch(ineq const& c) const;
+
+        bool proofs_enabled() const { return get_manager().proofs_enabled(); }
+        justification* justify(literal l1, literal l2);
+        justification* justify(literal_vector const& lits);
+
     public:
         theory_pb(ast_manager& m, theory_pb_params& p);