diff --git a/src/muz/dataflow/dataflow.h b/src/muz/dataflow/dataflow.h
index 1e52c5f93..d2be194eb 100644
--- a/src/muz/dataflow/dataflow.h
+++ b/src/muz/dataflow/dataflow.h
@@ -72,7 +72,7 @@ namespace datalog {
                     }
                     e->get_data().m_value->push_back(cur);
                 }
-                if (cur->get_uninterpreted_tail_size() == 0) {
+                if (cur->get_positive_tail_size() == 0) {
                     func_decl *sym = cur->get_head()->get_decl();
                     bool new_info = m_facts.insert_if_not_there2(sym, Fact())->get_data().m_value.init_up(m_context, cur);
                     if (new_info) {
@@ -97,7 +97,7 @@ namespace datalog {
         }
 
         void step_bottom_up() {
-            for(todo_set::iterator I = m_todo[m_todo_idx].begin(),
+            for(todo_set::iterator I = m_todo[m_todo_idx].begin(),                    
                 E = m_todo[m_todo_idx].end(); I!=E; ++I) {
                 ptr_vector<rule> * rules; 
                 if (!m_body2rules.find(*I, rules))
@@ -236,7 +236,7 @@ namespace datalog {
             return m_facts.get(m_rule->get_decl(idx), Fact::null_fact);
         }
         unsigned size() const {
-            return m_rule->get_uninterpreted_tail_size();
+            return m_rule->get_positive_tail_size();
         }
     };
 
diff --git a/src/muz/transforms/dl_mk_coi_filter.cpp b/src/muz/transforms/dl_mk_coi_filter.cpp
index e3d01a537..0f155f65b 100644
--- a/src/muz/transforms/dl_mk_coi_filter.cpp
+++ b/src/muz/transforms/dl_mk_coi_filter.cpp
@@ -44,9 +44,7 @@ namespace datalog {
                 if (m_context.has_facts(r->get_decl(i))) {
                     return 0;
                 }
-                if (false && r->is_neg_tail(i)) {
-                    return 0;
-                }
+
                 if (r->is_neg_tail(i)) {
                     if (!engine.get_fact(r->get_decl(i)).is_reachable()) {
                         if (!new_tail) {
@@ -62,6 +60,7 @@ namespace datalog {
                         m_new_tail_neg.push_back(true);
                     }
                 } 
+
                 else {
                     SASSERT(!new_tail);
                     if (!engine.get_fact(r->get_decl(i)).is_reachable()) {