diff --git a/src/cmd_context/tactic_cmds.cpp b/src/cmd_context/tactic_cmds.cpp
index 158f361dd..4febb1597 100644
--- a/src/cmd_context/tactic_cmds.cpp
+++ b/src/cmd_context/tactic_cmds.cpp
@@ -167,7 +167,7 @@ public:
 
 struct check_sat_tactic_result : public simple_check_sat_result {
 public:
-  svector<symbol> labels;
+  labels_vec labels;
 
   check_sat_tactic_result(ast_manager & m) : simple_check_sat_result(m) {
   }
@@ -181,8 +181,6 @@ public:
   }
 };
 
-typedef svector<symbol> & labels_ref;
-
 class check_sat_using_tactict_cmd : public exec_given_tactic_cmd {
 public:
     check_sat_using_tactict_cmd():
@@ -205,7 +203,7 @@ public:
         ast_manager & m = ctx.m();
         unsigned timeout   = p.get_uint("timeout", ctx.params().m_timeout);
         unsigned rlimit  =   p.get_uint("rlimit", ctx.params().m_rlimit);
-        svector<symbol> labels;
+        labels_vec labels;
         goal_ref g = alloc(goal, m, ctx.produce_proofs(), ctx.produce_models(), ctx.produce_unsat_cores());
         assert_exprs_from(ctx, *g);
         TRACE("check_sat_using", g->display(tout););
diff --git a/src/solver/tactic2solver.cpp b/src/solver/tactic2solver.cpp
index 586d59d4f..6b1a7916f 100644
--- a/src/solver/tactic2solver.cpp
+++ b/src/solver/tactic2solver.cpp
@@ -144,7 +144,7 @@ lbool tactic2solver::check_sat_core(unsigned num_assumptions, expr * const * ass
     proof_ref           pr(m);
     expr_dependency_ref core(m);
     std::string         reason_unknown = "unknown";
-    svector<symbol> labels;
+    labels_vec labels;
     try {
         switch (::check_sat(*m_tactic, g, md, labels, pr, core, reason_unknown)) {
         case l_true: 
diff --git a/src/tactic/model_converter.cpp b/src/tactic/model_converter.cpp
index efe80f226..6f6dd3da1 100644
--- a/src/tactic/model_converter.cpp
+++ b/src/tactic/model_converter.cpp
@@ -33,7 +33,7 @@ public:
         this->m_c1->operator()(m, 0);
     }
 
-    virtual void operator()(svector<symbol> & r, unsigned goal_idx) {
+    virtual void operator()(labels_vec & r, unsigned goal_idx) {
         this->m_c2->operator()(r, goal_idx);
         this->m_c1->operator()(r, 0);
     }
@@ -83,7 +83,7 @@ public:
         UNREACHABLE();
     }
 
-    virtual void operator()(svector<symbol> & r, unsigned goal_idx) {
+    virtual void operator()(labels_vec & r, unsigned goal_idx) {
         unsigned num = this->m_c2s.size();
         for (unsigned i = 0; i < num; i++) {
             if (goal_idx < this->m_szs[i]) {
@@ -142,7 +142,7 @@ public:
         m = m_model;
     }
 
-    virtual void operator()(svector<symbol> & r, unsigned goal_idx) {
+    virtual void operator()(labels_vec & r, unsigned goal_idx) {
       r.append(m_labels.size(), m_labels.c_ptr());
     }
 
diff --git a/src/tactic/model_converter.h b/src/tactic/model_converter.h
index 4395fc546..e2bc3cf83 100644
--- a/src/tactic/model_converter.h
+++ b/src/tactic/model_converter.h
@@ -23,6 +23,8 @@ Notes:
 #include"converter.h"
 #include"ref.h"
 
+class labels_vec : public svector<symbol> {};
+
 class model_converter : public converter {
 public:
     virtual void operator()(model_ref & m) {}  // TODO: delete
@@ -33,7 +35,7 @@ public:
         operator()(m);
     }
 
-    virtual void operator()(svector<symbol> & r, unsigned goal_idx) {}
+    virtual void operator()(labels_vec & r, unsigned goal_idx) {}
     
     virtual model_converter * translate(ast_translation & translator) = 0;
 };
diff --git a/src/tactic/tactic.cpp b/src/tactic/tactic.cpp
index 6eec018c7..0a95e8f65 100644
--- a/src/tactic/tactic.cpp
+++ b/src/tactic/tactic.cpp
@@ -174,7 +174,7 @@ void exec(tactic & t, goal_ref const & in, goal_ref_buffer & result, model_conve
     }
 }
 
-lbool check_sat(tactic & t, goal_ref & g, model_ref & md, svector<symbol> & labels, proof_ref & pr, expr_dependency_ref & core, std::string & reason_unknown) {
+lbool check_sat(tactic & t, goal_ref & g, model_ref & md, labels_vec & labels, proof_ref & pr, expr_dependency_ref & core, std::string & reason_unknown) {
     bool models_enabled = g->models_enabled();
     bool proofs_enabled = g->proofs_enabled();
     bool cores_enabled  = g->unsat_core_enabled();
diff --git a/src/tactic/tactic.h b/src/tactic/tactic.h
index 7c65c83e5..645b53681 100644
--- a/src/tactic/tactic.h
+++ b/src/tactic/tactic.h
@@ -153,7 +153,7 @@ public:
 #define MK_SIMPLE_TACTIC_FACTORY(NAME, ST)  MK_TACTIC_FACTORY(NAME, return ST;)
 
 void exec(tactic & t, goal_ref const & in, goal_ref_buffer & result, model_converter_ref & mc, proof_converter_ref & pc, expr_dependency_ref & core);
-lbool check_sat(tactic & t, goal_ref & g, model_ref & md, svector<symbol> & labels, proof_ref & pr, expr_dependency_ref & core, std::string & reason_unknown);
+lbool check_sat(tactic & t, goal_ref & g, model_ref & md, labels_vec & labels, proof_ref & pr, expr_dependency_ref & core, std::string & reason_unknown);
 
 // Throws an exception if goal \c in requires proof generation.
 void fail_if_proof_generation(char const * tactic_name, goal_ref const & in);