diff --git a/src/ast/ast.cpp b/src/ast/ast.cpp
index a74f87142..735079350 100644
--- a/src/ast/ast.cpp
+++ b/src/ast/ast.cpp
@@ -2038,11 +2038,13 @@ app * ast_manager::mk_app_core(func_decl * decl, unsigned num_args, expr * const
                 }
             }
         }
+        check_args(decl, num_args, new_args.c_ptr());
         SASSERT(new_args.size() == num_args);
         new_node = new (mem) app(decl, num_args, new_args.c_ptr());
         r = register_node(new_node);
     }
     else {
+        check_args(decl, num_args, args);
         new_node = new (mem) app(decl, num_args, args);
         r = register_node(new_node);
     }
@@ -2064,6 +2066,22 @@ app * ast_manager::mk_app_core(func_decl * decl, unsigned num_args, expr * const
     return r;
 }
 
+void ast_manager::check_args(func_decl* f, unsigned n, expr* const* es) {
+    for (unsigned i = 0; i < n; i++) {
+        sort * actual_sort   = get_sort(es[i]);
+        sort * expected_sort = f->is_associative() ? f->get_domain(0) : f->get_domain(i);
+        if (expected_sort != actual_sort) {
+            std::ostringstream buffer;
+            buffer << "Sort mismatch at argument #" << (i+1) 
+                   << " for function " << mk_pp(f,*this) 
+                   << " supplied sort is " 
+                   << mk_pp(actual_sort, *this);
+            throw ast_exception(buffer.str().c_str());            
+        }
+    }
+}
+
+
 inline app * ast_manager::mk_app_core(func_decl * decl, expr * arg1, expr * arg2) {
     expr * args[2] = { arg1, arg2 };
     return mk_app_core(decl, 2, args);
diff --git a/src/ast/ast.h b/src/ast/ast.h
index 214668536..c1ee603c7 100644
--- a/src/ast/ast.h
+++ b/src/ast/ast.h
@@ -1460,6 +1460,9 @@ protected:
 
     bool coercion_needed(func_decl * decl, unsigned num_args, expr * const * args);
 
+    void check_args(func_decl* f, unsigned n, expr* const* es);
+
+
 public:
     ast_manager(proof_gen_mode = PGM_DISABLED, char const * trace_file = 0, bool is_format_manager = false);
     ast_manager(proof_gen_mode, std::fstream * trace_stream, bool is_format_manager = false);
diff --git a/src/ast/pb_decl_plugin.cpp b/src/ast/pb_decl_plugin.cpp
index 36103c4f0..f4e3fdf97 100644
--- a/src/ast/pb_decl_plugin.cpp
+++ b/src/ast/pb_decl_plugin.cpp
@@ -280,3 +280,9 @@ bool pb_util::has_unit_coefficients(func_decl* f) const {
     }
     return true;
 }
+
+app* pb_util::mk_fresh_bool() {
+    symbol name = m.mk_fresh_var_name("pb");
+    func_decl_info info(m_fid, OP_PB_AUX_BOOL, 0, 0);
+    return m.mk_const(m.mk_func_decl(name, 0, (sort *const*)0, m.mk_bool_sort(), info));
+}
diff --git a/src/ast/pb_decl_plugin.h b/src/ast/pb_decl_plugin.h
index f38f577b3..d4264b9b9 100644
--- a/src/ast/pb_decl_plugin.h
+++ b/src/ast/pb_decl_plugin.h
@@ -35,6 +35,7 @@ enum pb_op_kind {
     OP_PB_LE,      // pseudo-Boolean <= (generalizes at_most_k)
     OP_PB_GE,      // pseudo-Boolean >= 
     OP_PB_EQ,      // equality
+    OP_PB_AUX_BOOL, // auxiliary internal Boolean variable.
     LAST_PB_OP
 };
 
@@ -71,6 +72,7 @@ public:
     virtual func_decl * mk_func_decl(decl_kind k, unsigned num_parameters, parameter const * parameters, 
                                      unsigned arity, sort * const * domain, sort * range);
     virtual void get_op_names(svector<builtin_name> & op_names, symbol const & logic);
+
 };
 
 
@@ -101,6 +103,7 @@ public:
     bool is_ge(func_decl* a) const;
     bool is_ge(expr* a) const { return is_app(a) && is_ge(to_app(a)->get_decl()); }
     bool is_ge(expr* a, rational& k) const;
+    bool is_aux_bool(expr* e) const { return is_app_of(e, m_fid, OP_PB_AUX_BOOL); }
     rational get_coeff(expr* a, unsigned index) const { return get_coeff(to_app(a)->get_decl(), index); }
     rational get_coeff(func_decl* a, unsigned index) const; 
     bool has_unit_coefficients(func_decl* f) const;
@@ -111,6 +114,8 @@ public:
     bool is_eq(expr* e) const { return is_app(e) && is_eq(to_app(e)->get_decl()); }
     bool is_eq(expr* e, rational& k) const;
 
+    app* mk_fresh_bool();
+
 
 private:
     rational to_rational(parameter const& p) const;
diff --git a/src/opt/opt_context.cpp b/src/opt/opt_context.cpp
index d50dd06d6..d7d96b2d1 100644
--- a/src/opt/opt_context.cpp
+++ b/src/opt/opt_context.cpp
@@ -31,7 +31,6 @@ Notes:
 #include "propagate_values_tactic.h"
 #include "solve_eqs_tactic.h"
 #include "elim_uncnstr_tactic.h"
-#include "elim_term_ite_tactic.h"
 #include "tactical.h"
 #include "model_smt2_pp.h"
 #include "card2bv_tactic.h"
@@ -652,7 +651,6 @@ namespace opt {
             and_then(mk_simplify_tactic(m), 
                      mk_propagate_values_tactic(m),
                      mk_solve_eqs_tactic(m),
-                     mk_elim_term_ite_tactic(m),
                      // NB: mk_elim_uncstr_tactic(m) is not sound with soft constraints
                      mk_simplify_tactic(m));   
         opt_params optp(m_params);
@@ -660,14 +658,16 @@ namespace opt {
         if (optp.elim_01()) {
             tac2 = mk_elim01_tactic(m);
             tac3 = mk_lia2card_tactic(m);
-            tac4 = mk_elim_term_ite_tactic(m);
             params_ref lia_p;
             lia_p.set_bool("compile_equality", optp.pb_compile_equality());
             tac3->updt_params(lia_p);
-            set_simplify(and_then(tac0.get(), tac2.get(), tac3.get(), tac4.get()));
+            set_simplify(and_then(tac0.get(), tac2.get(), tac3.get(), mk_simplify_tactic(m)));
         }
         else {
-            set_simplify(tac0.get());
+            tactic_ref tac1 = 
+                and_then(tac0.get(),
+                         mk_simplify_tactic(m));            
+            set_simplify(tac1.get());
         }
         proof_converter_ref pc;
         expr_dependency_ref core(m);
@@ -875,9 +875,11 @@ namespace opt {
                 TRACE("opt", tout << "maxsat: " << id << " offset:" << offset << "\n";);
             }
             else if (is_maximize(fml, tr, orig_term, index)) {
+                purify(tr);
                 m_objectives[index].m_term = tr;
             }
             else if (is_minimize(fml, tr, orig_term, index)) {
+                purify(tr);
                 m_objectives[index].m_term = tr;
                 m_objectives[index].m_adjust_value.set_negate(true);
             }
@@ -887,6 +889,50 @@ namespace opt {
         }
     }
 
+    void context::purify(app_ref& term) {
+        filter_model_converter_ref fm;
+        if (m_arith.is_add(term)) {
+            expr_ref_vector args(m);
+            unsigned sz = term->get_num_args();
+            for (unsigned i = 0; i < sz; ++i) {
+                expr* arg = term->get_arg(i);
+                if (is_mul_const(arg)) {
+                    args.push_back(arg);
+                }
+                else {
+                    args.push_back(purify(fm, arg));
+                }
+            }
+            term = m_arith.mk_add(args.size(), args.c_ptr());
+        }
+        else if (m_arith.is_arith_expr(term) && !is_mul_const(term)) {
+            TRACE("opt", tout << "Purifying " << term << "\n";);
+            term = purify(fm, term);
+        }
+        if (fm) {
+            m_model_converter = concat(m_model_converter.get(), fm.get());
+        }
+    }
+
+    bool context::is_mul_const(expr* e) {
+        expr* e1, *e2;
+        return 
+            is_uninterp_const(e) ||
+            m_arith.is_numeral(e) ||
+            (m_arith.is_mul(e, e1, e2) && m_arith.is_numeral(e1) && is_uninterp_const(e2)) ||
+            (m_arith.is_mul(e, e2, e1) && m_arith.is_numeral(e1) && is_uninterp_const(e2));
+    }
+
+    app* context::purify(filter_model_converter_ref& fm, expr* term) {
+       std::ostringstream out;
+       out << mk_pp(term, m);
+       app* q = m.mk_fresh_const(out.str().c_str(), m.get_sort(term));
+       if (!fm) fm = alloc(filter_model_converter, m);
+       m_hard_constraints.push_back(m.mk_eq(q, term));
+       fm->insert(q->get_decl());                
+       return q;
+    }
+
     /**
        To select the proper theory solver we have to ensure that all theory 
        symbols from soft constraints are reflected in the hard constraints.
@@ -894,7 +940,7 @@ namespace opt {
        - filter "obj" from generated model.
      */
     void context::mk_atomic(expr_ref_vector& terms) {
-        ref<filter_model_converter> fm;
+        filter_model_converter_ref fm;
         for (unsigned i = 0; i < terms.size(); ++i) {
             expr_ref p(terms[i].get(), m);
             app_ref q(m);
@@ -902,11 +948,7 @@ namespace opt {
                 terms[i] = p;
             }
             else {
-                q = m.mk_fresh_const("obj", m.mk_bool_sort()); 
-                terms[i] = q;
-                m_hard_constraints.push_back(m.mk_iff(p, q));
-                if (!fm) fm = alloc(filter_model_converter, m);
-                fm->insert(q->get_decl());
+                terms[i] = purify(fm, p);
             }
         }
         if (fm) {
diff --git a/src/opt/opt_context.h b/src/opt/opt_context.h
index 315e2473a..d17cc3748 100644
--- a/src/opt/opt_context.h
+++ b/src/opt/opt_context.h
@@ -244,6 +244,9 @@ namespace opt {
         bool is_maxsat(expr* fml, expr_ref_vector& terms, 
                        vector<rational>& weights, rational& offset, bool& neg, 
                        symbol& id, unsigned& index);
+        void  purify(app_ref& term);
+        app* purify(filter_model_converter_ref& fm, expr* e);
+        bool is_mul_const(expr* e);
         expr* mk_maximize(unsigned index, app* t);
         expr* mk_minimize(unsigned index, app* t);
         expr* mk_maxsat(unsigned index, unsigned num_fmls, expr* const* fmls);
diff --git a/src/smt/theory_pb.cpp b/src/smt/theory_pb.cpp
index 7be53ff86..c82076e87 100644
--- a/src/smt/theory_pb.cpp
+++ b/src/smt/theory_pb.cpp
@@ -410,18 +410,24 @@ namespace smt {
     }
 
     bool theory_pb::internalize_atom(app * atom, bool gate_ctx) {
-        SASSERT(m_util.is_at_most_k(atom) || m_util.is_le(atom) || 
-                m_util.is_ge(atom) || m_util.is_at_least_k(atom) || 
-                m_util.is_eq(atom));
-
         context& ctx = get_context();
         if (ctx.b_internalized(atom)) {
             return false;
         }
-
         SASSERT(!ctx.b_internalized(atom));
         m_stats.m_num_predicates++;
 
+        if (m_util.is_aux_bool(atom)) {
+            bool_var abv = ctx.mk_bool_var(atom);
+            ctx.set_var_theory(abv, get_id());
+            return true;
+        }
+        SASSERT(m_util.is_at_most_k(atom) || m_util.is_le(atom) || 
+                m_util.is_ge(atom) || m_util.is_at_least_k(atom) || 
+                m_util.is_eq(atom));
+
+
+
         unsigned num_args = atom->get_num_args();
         bool_var abv = ctx.mk_bool_var(atom);
         ctx.set_var_theory(abv, get_id());
@@ -617,15 +623,15 @@ namespace smt {
         // function internalize, where enodes for each argument
         // is available. 
         if (!has_bv) {
-            expr_ref tmp(m), fml(m);
-            tmp = m.mk_fresh_const("pb_proxy",m.mk_bool_sort());
+            app_ref tmp(m), fml(m);
+            pb_util pb(m);
+            tmp = pb.mk_fresh_bool();
             fml = m.mk_iff(tmp, arg);
             TRACE("pb", tout << "create proxy " << fml << "\n";);
             ctx.internalize(fml, false);
             SASSERT(ctx.b_internalized(tmp));
             bv = ctx.get_bool_var(tmp);
-            SASSERT(null_theory_var == ctx.get_var_theory(bv));
-            ctx.set_var_theory(bv, get_id());
+            SASSERT(get_id() == ctx.get_var_theory(bv));
             literal lit(ctx.get_bool_var(fml));
             ctx.mk_th_axiom(get_id(), 1, &lit);
             ctx.mark_as_relevant(tmp.get());
@@ -1148,17 +1154,19 @@ namespace smt {
         context&     ctx;
         ast_manager& m;
         theory_pb&   th;
+        pb_util      pb;
         typedef smt::literal literal;
         typedef smt::literal_vector literal_vector;
       
         psort_expr(context& c, theory_pb& th):
             ctx(c), 
             m(c.get_manager()),
-            th(th) {}
+            th(th),
+            pb(m) {}
 
         literal fresh() {
             app_ref y(m);
-            y = m.mk_fresh_const("y", m.mk_bool_sort());
+            y = pb.mk_fresh_bool();
             return literal(ctx.mk_bool_var(y));
         }
         
diff --git a/src/tactic/filter_model_converter.h b/src/tactic/filter_model_converter.h
index 0113e9fd9..6fc8fdd77 100644
--- a/src/tactic/filter_model_converter.h
+++ b/src/tactic/filter_model_converter.h
@@ -45,4 +45,6 @@ public:
     virtual model_converter * translate(ast_translation & translator);
 };
 
+typedef ref<filter_model_converter> filter_model_converter_ref;
+
 #endif