diff --git a/src/smt/smt_case_split_queue.cpp b/src/smt/smt_case_split_queue.cpp
index 41a269820..c461b130b 100644
--- a/src/smt/smt_case_split_queue.cpp
+++ b/src/smt/smt_case_split_queue.cpp
@@ -51,9 +51,9 @@ namespace smt {
             if (!m_theory_var_priority.find(v2, p_v2)) {
                 p_v2 = 0.0;
             }
-        // add clause activity
-        p_v1 += m_activity[v1];
-        p_v2 += m_activity[v2];
+            // add clause activity
+            p_v1 += m_activity[v1];
+            p_v2 += m_activity[v2];
             return p_v1 > p_v2;
         }
     };
@@ -82,6 +82,7 @@ namespace smt {
 
         virtual void mk_var_eh(bool_var v) {
             m_queue.reserve(v+1);
+            SASSERT(!m_queue.contains(v));
             m_queue.insert(v);
         }
 
@@ -130,10 +131,7 @@ namespace smt {
 
         virtual void display(std::ostream & out) {
             bool first = true;
-            bool_var_act_queue::const_iterator it  = m_queue.begin();
-            bool_var_act_queue::const_iterator end = m_queue.end();
-            for (; it != end ; ++it) {
-                unsigned v = *it;
+            for (unsigned v : m_queue) {
                 if (m_context.get_assignment(v) == l_undef) {
                     if (first) {
                         out << "remaining case-splits:\n";
@@ -143,8 +141,7 @@ namespace smt {
                 }
             }
             if (!first)
-                out << "\n";
-
+                out << "\n";            
         }
 
         virtual ~act_case_split_queue() {};
@@ -166,11 +163,15 @@ namespace smt {
             act_case_split_queue::activity_increased_eh(v);
             if (m_queue.contains(v))
                 m_queue.decreased(v);
+            if (m_delayed_queue.contains(v))
+                m_delayed_queue.decreased(v);
         }
 
         virtual void mk_var_eh(bool_var v) {
             m_queue.reserve(v+1);
             m_delayed_queue.reserve(v+1);
+            SASSERT(!m_delayed_queue.contains(v));
+            SASSERT(!m_queue.contains(v));
             if (m_context.is_searching()) 
                 m_delayed_queue.insert(v);
             else
@@ -1099,8 +1100,6 @@ namespace smt {
 #endif
 
             GOAL_STOP();
-
-            //std::cout << "goal set, time " << m_goal_time.get_seconds() << "\n";
         }
 
         void set_global_generation()
diff --git a/src/smt/smt_context.cpp b/src/smt/smt_context.cpp
index 4e56d3004..b5789a597 100644
--- a/src/smt/smt_context.cpp
+++ b/src/smt/smt_context.cpp
@@ -1826,6 +1826,7 @@ namespace smt {
     }
     
     void context::rescale_bool_var_activity() {
+        TRACE("case_split", tout << "rescale\n";);
         svector<double>::iterator it  = m_activity.begin();
         svector<double>::iterator end = m_activity.end();
         for (; it != end; ++it)
diff --git a/src/smt/smt_context.h b/src/smt/smt_context.h
index 9c70f5999..6b3129d91 100644
--- a/src/smt/smt_context.h
+++ b/src/smt/smt_context.h
@@ -1040,6 +1040,7 @@ namespace smt {
             if (act > ACTIVITY_LIMIT)
                 rescale_bool_var_activity();
             m_case_split_queue->activity_increased_eh(v);
+            TRACE("case_split", tout << "v" << v << " " << m_bvar_inc << " -> " << act << "\n";);
         }
 
     protected:
diff --git a/src/util/heap.h b/src/util/heap.h
index e8964a4f0..cde2451db 100644
--- a/src/util/heap.h
+++ b/src/util/heap.h
@@ -43,6 +43,15 @@ class heap : private LT {
         return i >> 1; 
     }
 
+    void display(std::ostream& out, unsigned indent, int idx) const {
+        if (idx < static_cast<int>(m_values.size())) {
+            for (unsigned i = 0; i < indent; ++i) out << " ";
+            out << m_values[idx] << "\n";
+            display(out, indent + 1, left(idx));
+            display(out, indent + 1, right(idx));
+        }
+    }
+
 #ifdef Z3DEBUG
     // Return true if the value can be inserted in the heap. That is, the vector m_value2indices is big enough to store this value.
     bool is_valid_value(int v) const { 
@@ -59,10 +68,13 @@ class heap : private LT {
         }
         return true;
     }
+
+
 public:
     bool check_invariant() const { 
         return check_invariant_core(1); 
     }
+
 #endif
 private:
 
@@ -219,6 +231,7 @@ public:
 
     void insert(int val) {
         CASSERT("heap", check_invariant());
+        CASSERT("heap", !contains(val));
         SASSERT(is_valid_value(val));
         int idx              = static_cast<int>(m_values.size());
         m_value2indices[val] = idx;
@@ -272,6 +285,11 @@ public:
             }
         }
     }
+
+    void display(std::ostream& out) const {
+        display(out, 0, 1);
+    }
+
   
 };