diff --git a/src/ast/sls/sls_arith_base.cpp b/src/ast/sls/sls_arith_base.cpp
index 60d65c5a6..259bb49d9 100644
--- a/src/ast/sls/sls_arith_base.cpp
+++ b/src/ast/sls/sls_arith_base.cpp
@@ -1416,6 +1416,7 @@ namespace sls {
         buffer<var_t> todo;
         todo.push_back(v);
         auto& vi = m_vars[v];
+        m_tmp_set.reset();
         for (unsigned i = 0; i < todo.size(); ++i) {
             var_t u = todo[i];
             auto& ui = m_vars[u];
@@ -1434,8 +1435,10 @@ namespace sls {
                     todo.push_back(x);
             }
             for (auto const& [coeff, bv] : ui.m_linear_occurs)
-                vi.m_bool_vars_of.insert(bv);
+                m_tmp_set.insert(bv);
         }
+        for (auto bv : m_tmp_set)
+            vi.m_bool_vars_of.push_back(bv);
     }
 
     template<typename num_t>
diff --git a/src/ast/sls/sls_arith_base.h b/src/ast/sls/sls_arith_base.h
index 2c7cf0c7f..bb0a013bc 100644
--- a/src/ast/sls/sls_arith_base.h
+++ b/src/ast/sls/sls_arith_base.h
@@ -119,7 +119,7 @@ namespace sls {
             arith_op_kind m_op = arith_op_kind::LAST_ARITH_OP;
             unsigned     m_def_idx = UINT_MAX;
             vector<std::pair<num_t, sat::bool_var>> m_linear_occurs;
-            indexed_uint_set m_bool_vars_of;
+            sat::bool_var_vector m_bool_vars_of;
             unsigned_vector m_muls;
             unsigned_vector m_adds;
             optional<bound> m_lo, m_hi;
@@ -215,6 +215,7 @@ namespace sls {
         arith_clausal<num_t>         m_clausal_sls;
         svector<double>              m_prob_break;
         indexed_uint_set             m_bool_var_atoms;
+        indexed_uint_set             m_tmp_set;
 
         void invariant();
         void invariant(ineq const& i);