diff --git a/src/math/lp/lar_solver.cpp b/src/math/lp/lar_solver.cpp
index c5396b2f9..6f9c14bc7 100644
--- a/src/math/lp/lar_solver.cpp
+++ b/src/math/lp/lar_solver.cpp
@@ -1365,7 +1365,7 @@ void lar_solver::pop() {
 }
 
 bool lar_solver::column_represents_row_in_tableau(unsigned j) {
-    return m_columns_to_ul_pairs()[j].m_i != UINT_MAX;
+    return m_columns_to_ul_pairs()[j].associated_with_row();
 }
 
 void lar_solver::make_sure_that_the_bottom_right_elem_not_zero_in_tableau(unsigned i, unsigned j) {
@@ -1602,7 +1602,7 @@ var_index lar_solver::add_var(unsigned ext_j, bool is_int) {
         return local_j;    
     lp_assert(m_columns_to_ul_pairs.size() == A_r().column_count());
     local_j = A_r().column_count();
-    m_columns_to_ul_pairs.push_back(ul_pair(UINT_MAX));
+    m_columns_to_ul_pairs.push_back(ul_pair(false)); // not associated with a row
     while (m_usage_in_terms.size() <= ext_j) {
         m_usage_in_terms.push_back(0);
     }
@@ -1628,7 +1628,7 @@ void lar_solver::add_non_basic_var_to_core_fields(unsigned ext_j, bool is_int) {
     register_new_ext_var_index(ext_j, is_int);
     m_mpq_lar_core_solver.m_column_types.push_back(column_type::free_column);
     m_columns_with_changed_bound.increase_size_by_one();
-    add_new_var_to_core_fields_for_mpq(false);
+    add_new_var_to_core_fields_for_mpq(false); // false for not adding a row
     if (use_lu())
         add_new_var_to_core_fields_for_doubles(false);
 }
@@ -1759,7 +1759,7 @@ void lar_solver::add_row_from_term_no_constraint(const lar_term * term, unsigned
     register_new_ext_var_index(term_ext_index, term_is_int(term));
     // j will be a new variable
     unsigned j = A_r().column_count();
-    ul_pair ul(j);
+    ul_pair ul(true); // to mark this column as associated_with_row
     m_columns_to_ul_pairs.push_back(ul);
     add_basic_var_to_core_fields();
     if (use_tableau()) {
diff --git a/src/math/lp/ul_pair.h b/src/math/lp/ul_pair.h
index e40fe98f8..371b507ac 100644
--- a/src/math/lp/ul_pair.h
+++ b/src/math/lp/ul_pair.h
@@ -50,12 +50,12 @@ inline bool compare(const std::pair<mpq, var_index> & a, const std::pair<mpq, va
 class ul_pair {
     constraint_index m_lower_bound_witness;
     constraint_index m_upper_bound_witness;
+    bool             m_associated_with_row;  
 public:
     constraint_index& lower_bound_witness() {return m_lower_bound_witness;}
     constraint_index lower_bound_witness() const {return m_lower_bound_witness;}
     constraint_index& upper_bound_witness() { return m_upper_bound_witness;}
     constraint_index upper_bound_witness() const {return m_upper_bound_witness;}
-    row_index m_i;
     bool operator!=(const ul_pair & p) const {
         return !(*this == p);
     }
@@ -63,19 +63,24 @@ public:
     bool operator==(const ul_pair & p) const {
         return m_lower_bound_witness == p.m_lower_bound_witness
             && m_upper_bound_witness == p.m_upper_bound_witness &&
-            m_i == p.m_i;
+            m_associated_with_row == p.m_associated_with_row;
     }
     // empty constructor
     ul_pair() :
-        m_lower_bound_witness(static_cast<constraint_index>(-1)),
-        m_upper_bound_witness(static_cast<constraint_index>(-1)),
-        m_i(static_cast<row_index>(-1))
-    {}
-    ul_pair(row_index ri) :
-        m_lower_bound_witness(static_cast<constraint_index>(-1)),
-        m_upper_bound_witness(static_cast<constraint_index>(-1)),
-        m_i(ri) {}
-    ul_pair(const ul_pair & o): m_lower_bound_witness(o.m_lower_bound_witness), m_upper_bound_witness(o.m_upper_bound_witness), m_i(o.m_i) {}
+        m_lower_bound_witness(UINT_MAX),
+        m_upper_bound_witness(UINT_MAX),
+        m_associated_with_row(false) {}
+    
+    ul_pair(bool associated_with_row) :
+        m_lower_bound_witness(UINT_MAX),
+        m_upper_bound_witness(UINT_MAX),
+        m_associated_with_row(associated_with_row) {}
+    
+    ul_pair(const ul_pair & o):
+        m_lower_bound_witness(o.m_lower_bound_witness),
+        m_upper_bound_witness(o.m_upper_bound_witness),
+        m_associated_with_row(o.m_associated_with_row) {}
+    bool associated_with_row() const { return m_associated_with_row; }
 };
 
 }
diff --git a/src/smt/params/smt_params_helper.pyg b/src/smt/params/smt_params_helper.pyg
index 25e611f4c..86db50e3c 100644
--- a/src/smt/params/smt_params_helper.pyg
+++ b/src/smt/params/smt_params_helper.pyg
@@ -41,7 +41,7 @@ def_module_params(module_name='smt',
                           ('bv.reflect', BOOL, True, 'create enode for every bit-vector term'),
                           ('bv.enable_int2bv', BOOL, True, 'enable support for int2bv and bv2int operators'),
                           ('arith.random_initial_value', BOOL, False, 'use random initial values in the simplex-based procedure for linear arithmetic'),
-                          ('arith.solver', UINT, 2, 'arithmetic solver: 0 - no solver, 1 - bellman-ford based solver (diff. logic only), 2 - simplex based solver, 3 - floyd-warshall based solver (diff. logic only) and no theory combination 4 - utvpi, 5 - infinitary lra, 6 - lra solver'),
+                          ('arith.solver', UINT, 6, 'arithmetic solver: 0 - no solver, 1 - bellman-ford based solver (diff. logic only), 2 - simplex based solver, 3 - floyd-warshall based solver (diff. logic only) and no theory combination 4 - utvpi, 5 - infinitary lra, 6 - lra solver'),
                           ('arith.nl', BOOL, True, '(incomplete) nonlinear arithmetic support based on Groebner basis and interval propagation, relevant only if smt.arith.solver=2'),
                           ('arith.nl.gb', BOOL, True, 'groebner Basis computation, this option is ignored when arith.nl=false, relevant only if smt.arith.solver=2'),
                           ('arith.nl.branching', BOOL, True, 'branching on integer variables in non linear clusters, relevant only if smt.arith.solver=2'),