diff --git a/src/library/tactic/justification_builder.h b/src/library/tactic/justification_builder.h
deleted file mode 100644
index d775161fb1..0000000000
--- a/src/library/tactic/justification_builder.h
+++ /dev/null
@@ -1,52 +0,0 @@
-/*
-Copyright (c) 2013 Microsoft Corporation. All rights reserved.
-Released under Apache 2.0 license as described in the file LICENSE.
-
-Author: Leonardo de Moura
-*/
-#pragma once
-#include <algorithm>
-#include "util/name.h"
-#include "util/rc.h"
-#include "kernel/expr.h"
-#include "kernel/justification.h"
-#include "library/tactic/assignment.h"
-
-namespace lean {
-class justification_builder_cell {
-    void dealloc() { delete this; }
-    MK_LEAN_RC();
-public:
-    virtual ~justification_builder_cell() {}
-    virtual justification operator()(name const & n, justification const & j, environment const & env, assignment const & a) const = 0;
-};
-
-class justification_builder {
-protected:
-    justification_builder_cell * m_ptr;
-public:
-    justification_builder():m_ptr(nullptr) {}
-    explicit justification_builder(justification_builder_cell * ptr):m_ptr(ptr) { lean_assert(m_ptr); m_ptr->inc_ref(); }
-    justification_builder(justification_builder const & s):m_ptr(s.m_ptr) { if (m_ptr) m_ptr->inc_ref(); }
-    justification_builder(justification_builder && s):m_ptr(s.m_ptr) { s.m_ptr = nullptr; }
-    ~justification_builder() { if (m_ptr) m_ptr->dec_ref(); }
-    friend void swap(justification_builder & a, justification_builder & b) { std::swap(a.m_ptr, b.m_ptr); }
-    justification_builder & operator=(justification_builder const & s) { LEAN_COPY_REF(justification_builder, s); }
-    justification_builder & operator=(justification_builder && s) { LEAN_MOVE_REF(justification_builder, s); }
-
-    justification operator()(name const & n, justification const & j, environment const & env, assignment const & a) const { return m_ptr->operator()(n, j, env, a); }
-};
-
-template<typename F>
-class simple_justification_builder : public justification_builder_cell {
-    F m_f;
-public:
-    simple_justification_builder(F && f):m_f(std::forward<F>(f)) {}
-    virtual justification operator()(name const & n, justification const & j, environment const & env, assignment const & a) const { return m_f(n, j, env, a); }
-};
-
-template<typename F>
-justification_builder mk_justification_builder(F && f) {
-    return justification_builder(new simple_justification_builder<F>(std::forward<F>(f)));
-}
-}
diff --git a/src/library/tactic/proof_state.cpp b/src/library/tactic/proof_state.cpp
index 9b486baeda..628ec6904f 100644
--- a/src/library/tactic/proof_state.cpp
+++ b/src/library/tactic/proof_state.cpp
@@ -26,7 +26,6 @@ void swap(proof_state & s1, proof_state & s2) {
     swap(s1.m_goals, s2.m_goals);
     swap(s1.m_menv, s2.m_menv);
     swap(s1.m_proof_builder, s2.m_proof_builder);
-    swap(s1.m_justification_builder, s2.m_justification_builder);
 }
 
 static name g_main("main");
@@ -42,12 +41,6 @@ proof_state to_proof_state(environment const & env, context const & ctx, expr co
                 throw tactic_exception(sstream() << "failed to find proof for '" << g_main << "' goal");
             return fn(p);
         });
-    justification_builder j = mk_justification_builder(
-        [](name const & n, justification const & j, environment const &, assignment const &) -> justification {
-            if (n != g_main)
-                throw tactic_exception(sstream() << "unknown goal name '" << n << "'");
-            return j;
-        });
-    return proof_state(goals(mk_pair(g_main, g)), metavar_env(), p, j);
+    return proof_state(goals(mk_pair(g_main, g)), metavar_env(), p);
 }
 }
diff --git a/src/library/tactic/proof_state.h b/src/library/tactic/proof_state.h
index a1b61d32bd..15740eebcf 100644
--- a/src/library/tactic/proof_state.h
+++ b/src/library/tactic/proof_state.h
@@ -8,7 +8,6 @@ Author: Leonardo de Moura
 #include <utility>
 #include "library/tactic/goal.h"
 #include "library/tactic/proof_builder.h"
-#include "library/tactic/justification_builder.h"
 
 namespace lean {
 typedef list<std::pair<name, goal>> goals;
@@ -16,18 +15,16 @@ class proof_state {
     goals                       m_goals;
     metavar_env                 m_menv;
     proof_builder               m_proof_builder;
-    justification_builder       m_justification_builder;
 public:
     proof_state() {}
-    proof_state(list<std::pair<name, goal>> const & gs, metavar_env const & menv, proof_builder const & p, justification_builder const & j):
-        m_goals(gs), m_menv(menv), m_proof_builder(p), m_justification_builder(j) {}
+    proof_state(list<std::pair<name, goal>> const & gs, metavar_env const & menv, proof_builder const & p):
+        m_goals(gs), m_menv(menv), m_proof_builder(p) {}
     proof_state(proof_state const & s, goals const & gs, proof_builder const & p):
-        m_goals(gs), m_menv(s.m_menv), m_proof_builder(p), m_justification_builder(s.m_justification_builder) {}
+        m_goals(gs), m_menv(s.m_menv), m_proof_builder(p) {}
     friend void swap(proof_state & s1, proof_state & s2);
     list<std::pair<name, goal>> const & get_goals() const { return m_goals; }
     metavar_env const & get_menv() const { return m_menv; }
     proof_builder const & get_proof_builder() const { return m_proof_builder; }
-    justification_builder const & get_justification_builder() const { return m_justification_builder; }
     format pp(formatter const & fmt, options const & opts) const;
 };
 void swap(proof_state & s1, proof_state & s2);
diff --git a/src/library/tactic/tactic.cpp b/src/library/tactic/tactic.cpp
index 279d96a8e8..5cff2f8ded 100644
--- a/src/library/tactic/tactic.cpp
+++ b/src/library/tactic/tactic.cpp
@@ -60,6 +60,55 @@ expr tactic::solve(environment const & env, io_state const & io, proof_state con
     return final->get_proof_builder()(m, env, a);
 }
 
+expr tactic::solve(environment const & env, io_state const & io, context const & ctx, expr const & t) {
+    proof_state s = to_proof_state(env, ctx, t);
+    return solve(env, io, s);
+}
+
+tactic id_tactic() { return mk_tactic([](environment const &, io_state const &, proof_state const & s) -> proof_state { return s; }); }
+
+tactic fail_tactic() { return mk_tactic([](environment const &, io_state const &, proof_state const &) -> proof_state { throw tactic_exception("failed"); }); }
+
+tactic now_tactic() {
+    return mk_tactic([](environment const &, io_state const &, proof_state const & s) -> proof_state {
+            if (!empty(s.get_goals()))
+                throw tactic_exception("nowtac failed");
+            return s;
+        });
+}
+
+tactic assumption_tactic() {
+    return mk_tactic([](environment const &, io_state const &, proof_state const & s) -> proof_state {
+            list<std::pair<name, expr>> proofs;
+            goals new_goals = map_goals(s, [&](name const & ng, goal const & g) -> goal {
+                    expr const & c  = g.get_conclusion();
+                    expr pr;
+                    for (auto const & p : g.get_hypotheses()) {
+                        check_interrupted();
+                        if (p.second == c) {
+                            pr = mk_constant(p.first);
+                            break;
+                        }
+                    }
+                    if (pr) {
+                        proofs.emplace_front(ng, pr);
+                        return goal();
+                    } else {
+                        return g;
+                    }
+                });
+            proof_builder p     = s.get_proof_builder();
+            proof_builder new_p = mk_proof_builder([=](proof_map const & m, environment const & env, assignment const & a) -> expr {
+                    proof_map new_m(m);
+                    for (auto const & np : proofs) {
+                        new_m.insert(np.first, np.second);
+                    }
+                    return p(new_m, env, a);
+                });
+            return proof_state(s, new_goals, new_p);
+        });
+}
+
 class then_tactic : public tactic_cell {
     tactic m_t1;
     tactic m_t2;
@@ -106,48 +155,4 @@ public:
 };
 
 tactic then(tactic const & t1, tactic const & t2) { return tactic(new then_tactic(t1, t2)); }
-
-tactic id_tactic() { return mk_tactic([](environment const &, io_state const &, proof_state const & s) -> proof_state { return s; }); }
-
-tactic fail_tactic() { return mk_tactic([](environment const &, io_state const &, proof_state const &) -> proof_state { throw tactic_exception("failed"); }); }
-
-tactic now_tactic() {
-    return mk_tactic([](environment const &, io_state const &, proof_state const & s) -> proof_state {
-            if (!empty(s.get_goals()))
-                throw tactic_exception("nowtac failed");
-            return s;
-        });
-}
-
-tactic assumption_tactic() {
-    return mk_tactic([](environment const &, io_state const &, proof_state const & s) -> proof_state {
-            list<std::pair<name, expr>> proofs;
-            goals new_goals = map_goals(s, [&](name const & ng, goal const & g) -> goal {
-                    expr const & c  = g.get_conclusion();
-                    expr pr;
-                    for (auto const & p : g.get_hypotheses()) {
-                        check_interrupted();
-                        if (p.second == c) {
-                            pr = mk_constant(p.first);
-                            break;
-                        }
-                    }
-                    if (pr) {
-                        proofs.emplace_front(ng, pr);
-                        return goal();
-                    } else {
-                        return g;
-                    }
-                });
-            proof_builder p     = s.get_proof_builder();
-            proof_builder new_p = mk_proof_builder([=](proof_map const & m, environment const & env, assignment const & a) -> expr {
-                    proof_map new_m(m);
-                    for (auto const & np : proofs) {
-                        new_m.insert(np.first, np.second);
-                    }
-                    return p(new_m, env, a);
-                });
-            return proof_state(s, new_goals, new_p);
-        });
-}
 }
diff --git a/src/library/tactic/tactic.h b/src/library/tactic/tactic.h
index ede5b34539..43e1ce2646 100644
--- a/src/library/tactic/tactic.h
+++ b/src/library/tactic/tactic.h
@@ -58,6 +58,7 @@ public:
     tactic_result_ref operator()(proof_state const & s) { return m_ptr->operator()(s); }
 
     expr solve(environment const & env, io_state const & io, proof_state const & s);
+    expr solve(environment const & env, io_state const & io, context const & ctx, expr const & t);
 };
 
 template<typename F>
diff --git a/src/tests/library/tactic/tactic.cpp b/src/tests/library/tactic/tactic.cpp
index d49081946e..ef930224e1 100644
--- a/src/tests/library/tactic/tactic.cpp
+++ b/src/tests/library/tactic/tactic.cpp
@@ -9,9 +9,9 @@ Author: Leonardo de Moura
 #include "library/all/all.h"
 #include "library/tactic/goal.h"
 #include "library/tactic/proof_builder.h"
-#include "library/tactic/justification_builder.h"
 #include "library/tactic/proof_state.h"
 #include "library/tactic/tactic.h"
+#include "library/tactic/tactic_exception.h"
 using namespace lean;
 
 static void tst1() {
@@ -28,7 +28,14 @@ static void tst1() {
     proof_state s = to_proof_state(env, ctx, p);
     std::cout << s.pp(mk_simple_formatter(), options()) << "\n";
     tactic t = then(assumption_tactic(), now_tactic());
-    std::cout << "proof: " << t.solve(env, io, s) << "\n";
+    std::cout << "proof 1: " << t.solve(env, io, s) << "\n";
+    std::cout << "proof 2: " << t.solve(env, io, ctx, q) << "\n";
+    try {
+        now_tactic().solve(env, io, ctx, q);
+        lean_unreachable();
+    } catch (tactic_exception & ex) {
+        std::cout << "expected error: " << ex.what() << "\n";
+    }
 }
 
 int main() {