diff --git a/src/api/api_quant.cpp b/src/api/api_quant.cpp
index 883e9e752..4170852a9 100644
--- a/src/api/api_quant.cpp
+++ b/src/api/api_quant.cpp
@@ -165,7 +165,10 @@ extern "C" {
         }
         for (unsigned i = 0; i < num_bound; ++i) {
             app* a = to_app(bound[i]);
-            SASSERT(a->get_kind() == AST_APP);
+            if (a->get_kind() != AST_APP) {
+                SET_ERROR_CODE(Z3_INVALID_ARG);
+                RETURN_Z3(0);
+            }
             symbol s(to_app(a)->get_decl()->get_name());
             names.push_back(of_symbol(s));
             types.push_back(of_sort(mk_c(c)->m().get_sort(a)));
diff --git a/src/ast/rewriter/ast_counter.cpp b/src/ast/rewriter/ast_counter.cpp
index a807237c5..6f49a232f 100644
--- a/src/ast/rewriter/ast_counter.cpp
+++ b/src/ast/rewriter/ast_counter.cpp
@@ -108,6 +108,7 @@ void var_counter::count_vars(ast_manager & m, const app * pred, int coef) {
 unsigned var_counter::get_max_var(bool& has_var) {
     has_var = false;
     unsigned max_var = 0;
+    ptr_vector<quantifier> qs;
     while (!m_todo.empty()) {
         expr* e = m_todo.back();
         m_todo.pop_back();
@@ -117,14 +118,7 @@ unsigned var_counter::get_max_var(bool& has_var) {
         m_visited.mark(e, true);
         switch(e->get_kind()) {
         case AST_QUANTIFIER: {
-            var_counter aux_counter;
-            quantifier* q = to_quantifier(e);
-            bool has_var1 = false;
-            unsigned max_v = aux_counter.get_max_var(has_var1);
-            if (max_v > max_var + q->get_num_decls()) {
-                max_var = max_v - q->get_num_decls();
-                has_var = true;
-            }
+            qs.push_back(to_quantifier(e));
             break;                 
         }
         case AST_VAR: {
@@ -147,6 +141,20 @@ unsigned var_counter::get_max_var(bool& has_var) {
         }
     }
     m_visited.reset();
+
+    while (!qs.empty()) {
+        var_counter aux_counter;
+        quantifier* q = qs.back();
+        qs.pop_back();
+        aux_counter.m_todo.push_back(q->get_expr());
+        bool has_var1 = false;
+        unsigned max_v = aux_counter.get_max_var(has_var1);
+        if (max_v >= max_var + q->get_num_decls()) {
+            max_var = max_v - q->get_num_decls();
+            has_var = has_var || has_var1;                
+        }
+    }
+
     return max_var;
 }
 
diff --git a/src/muz_qe/dl_context.cpp b/src/muz_qe/dl_context.cpp
index 9f250742c..7da9808e7 100644
--- a/src/muz_qe/dl_context.cpp
+++ b/src/muz_qe/dl_context.cpp
@@ -652,6 +652,7 @@ namespace datalog {
             if (check_pred(e)) {
                 std::ostringstream out;
                 out << "recursive predicate " << mk_ismt2_pp(e, get_manager()) << " occurs nested in body";
+                r->display(*this, out << "\n");
                 throw default_exception(out.str());
 
             }
diff --git a/src/muz_qe/dl_rule.cpp b/src/muz_qe/dl_rule.cpp
index 70da4ed4b..455f2c244 100644
--- a/src/muz_qe/dl_rule.cpp
+++ b/src/muz_qe/dl_rule.cpp
@@ -186,15 +186,20 @@ namespace datalog {
     }
 
     void rule_manager::mk_rule_core(expr* fml, proof* p, rule_set& rules, symbol const& name) {
+        DEBUG_CODE(ptr_vector<sort> sorts; 
+                   ::get_free_vars(fml, sorts); );
         expr_ref_vector fmls(m);
         proof_ref_vector prs(m);
         m_hnf.reset();
         m_hnf.set_name(name);
+        
         m_hnf(fml, p, fmls, prs);
         for (unsigned i = 0; i < m_hnf.get_fresh_predicates().size(); ++i) {
             m_ctx.register_predicate(m_hnf.get_fresh_predicates()[i], false);
         }
         for (unsigned i = 0; i < fmls.size(); ++i) {
+            DEBUG_CODE(ptr_vector<sort> sorts; 
+                       ::get_free_vars(fmls[i].get(), sorts); );
             mk_horn_rule(fmls[i].get(), prs[i].get(), rules, name);
         }
     }
@@ -265,7 +270,7 @@ namespace datalog {
         } 
         else {
             head = ensure_app(fml);
-        }
+        }        
         return index;
     }
 
@@ -491,6 +496,12 @@ namespace datalog {
         app * * uninterp_tail = r->m_tail; //grows upwards
         app * * interp_tail = r->m_tail+n; //grows downwards
 
+        DEBUG_CODE(ptr_vector<sort> sorts; 
+                   ::get_free_vars(head, sorts);
+                   for (unsigned i = 0; i < n; ++i) {
+                       ::get_free_vars(tail[i], sorts);
+                   });
+
         bool has_neg = false;
 
         for (unsigned i = 0; i < n; i++) {
diff --git a/src/muz_qe/hnf.cpp b/src/muz_qe/hnf.cpp
index 75a85061c..36316cfa6 100644
--- a/src/muz_qe/hnf.cpp
+++ b/src/muz_qe/hnf.cpp
@@ -128,7 +128,12 @@ public:
     }
 
     void set_name(symbol const& n) {
-        m_name = n;
+        if (n == symbol::null) {
+            m_name = symbol("P");
+        }
+        else {
+            m_name = n;
+        }
     }
 
     func_decl_ref_vector const& get_fresh_predicates() {
diff --git a/src/muz_qe/rel_context.cpp b/src/muz_qe/rel_context.cpp
index ce1b30b88..d597500b2 100644
--- a/src/muz_qe/rel_context.cpp
+++ b/src/muz_qe/rel_context.cpp
@@ -105,14 +105,12 @@ namespace datalog {
         }        
     }
 
-    lbool rel_context::saturate() {
+    lbool rel_context::saturate(scoped_query& sq) {
         m_context.ensure_closed();        
         bool time_limit = m_context.soft_timeout()!=0;
         unsigned remaining_time_limit = m_context.soft_timeout();
         unsigned restart_time = m_context.initial_restart_timeout();
-        
-        scoped_query scoped_query(m_context);
-                
+                        
         instruction_block termination_code;
 
         lbool result;
@@ -191,7 +189,7 @@ namespace datalog {
             else {
                 restart_time = static_cast<unsigned>(new_restart_time);
             }
-            scoped_query.reset();
+            sq.reset();
         }
         m_context.record_transformed_rules();
         TRACE("dl", display_profile(tout););
@@ -206,7 +204,7 @@ namespace datalog {
         }
         m_context.close();
         reset_negated_tables();
-        lbool res = saturate();
+        lbool res = saturate(_scoped_query);
 
         switch(res) {
         case l_true: {
@@ -215,7 +213,8 @@ namespace datalog {
             bool some_non_empty = num_rels == 0;
             bool is_approx = false;
             for (unsigned i = 0; i < num_rels; ++i) {
-                relation_base& rel = get_relation(rels[i]);
+                func_decl* q = m_context.get_rules().get_pred(rels[i]);
+                relation_base& rel = get_relation(q);
                 if (!rel.empty()) {
                     some_non_empty = true;
                 }
@@ -272,13 +271,14 @@ namespace datalog {
 
         if (m_context.magic_sets_for_queries()) {
             m_context.transform_rules(alloc(mk_magic_sets, m_context, query_pred));
+            query_pred = m_context.get_rules().get_pred(query_pred);
         }
 
+        lbool res = saturate(_scoped_query);
+        
         query_pred = m_context.get_rules().get_pred(query_pred);
 
-        lbool res = saturate();
-        
-        if (res != l_undef) {
+        if (res != l_undef) {            
             m_last_result_relation = get_relation(query_pred).clone();
             if (m_last_result_relation->empty()) {
                 res = l_false;
diff --git a/src/muz_qe/rel_context.h b/src/muz_qe/rel_context.h
index 057d1c15f..0b73caaa6 100644
--- a/src/muz_qe/rel_context.h
+++ b/src/muz_qe/rel_context.h
@@ -109,7 +109,7 @@ namespace datalog {
 
         void display_profile(std::ostream& out);
 
-        lbool saturate();
+        lbool saturate(scoped_query& sq);
 
     };
 };