diff --git a/NEWS b/NEWS
index bb07e1899..595111478 100644
--- a/NEWS
+++ b/NEWS
@@ -93,6 +93,10 @@ New in spot 2.0.3a (not yet released)
     project a run found in a product onto one of the original operand.
     This is for instance used by autfilt --highlight-word.
 
+    The old spot::project_twa_run() function has been removed: it was
+    not used anywhere in Spot, and had an obvious bug in its
+    implementation, so it cannot be missed by anyone.
+
   Python:
 
   * The __format__() method for formula support the same
diff --git a/doc/org/upgrade2.org b/doc/org/upgrade2.org
index e2618e4f5..8df4ff21c 100644
--- a/doc/org/upgrade2.org
+++ b/doc/org/upgrade2.org
@@ -286,7 +286,7 @@ that provide a function with a similar service.
 | ~tgbaalgos/neverclaim.hh~          | ~spot/twaalgos/neverclaim.hh~      |                                                  |
 | ~tgbaalgos/postproc.hh~            | ~spot/twaalgos/postproc.hh~        |                                                  |
 | ~tgbaalgos/powerset.hh~            | ~spot/twaalgos/powerset.hh~        |                                                  |
-| ~tgbaalgos/projrun.hh~             | ~spot/twaalgos/projrun.hh~         |                                                  |
+| ~tgbaalgos/projrun.hh~             | ~spot/twaalgos/emptiness.hh~       | use =twa_run::project()= since Spot 2.1          |
 | ~tgbaalgos/randomgraph.hh~         | ~spot/twaalgos/randomgraph.hh~     |                                                  |
 | ~tgbaalgos/reachiter.hh~           | ~spot/twaalgos/reachiter.hh~       |                                                  |
 | ~tgbaalgos/reducerun.hh~           | ~spot/twaalgos/emptiness.hh~       | now =twa_run::reduce()=                          |
diff --git a/spot/twaalgos/Makefile.am b/spot/twaalgos/Makefile.am
index 48f0db39b..da694e374 100644
--- a/spot/twaalgos/Makefile.am
+++ b/spot/twaalgos/Makefile.am
@@ -59,7 +59,6 @@ twaalgos_HEADERS = \
   postproc.hh \
   powerset.hh \
   product.hh \
-  projrun.hh \
   randomgraph.hh \
   randomize.hh \
   reachiter.hh \
@@ -115,7 +114,6 @@ libtwaalgos_la_SOURCES = \
   postproc.cc \
   powerset.cc \
   product.cc \
-  projrun.cc \
   randomgraph.cc \
   randomize.cc \
   reachiter.cc \
diff --git a/spot/twaalgos/projrun.cc b/spot/twaalgos/projrun.cc
deleted file mode 100644
index e8f1564db..000000000
--- a/spot/twaalgos/projrun.cc
+++ /dev/null
@@ -1,44 +0,0 @@
-// -*- coding: utf-8 -*-
-// Copyright (C) 2014, 2015 Laboratoire de Recherche et Développement
-// de l'Epita (LRDE)
-// Copyright (C) 2004  Laboratoire d'Informatique de Paris 6 (LIP6),
-// département Systèmes Répartis Coopératifs (SRC), Université Pierre
-// et Marie Curie.
-//
-// This file is part of Spot, a model checking library.
-//
-// Spot is free software; you can redistribute it and/or modify it
-// under the terms of the GNU General Public License as published by
-// the Free Software Foundation; either version 3 of the License, or
-// (at your option) any later version.
-//
-// Spot is distributed in the hope that it will be useful, but WITHOUT
-// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
-// or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
-// License for more details.
-//
-// You should have received a copy of the GNU General Public License
-// along with this program.  If not, see <http://www.gnu.org/licenses/>.
-
-#include <spot/twaalgos/projrun.hh>
-#include <spot/twa/twa.hh>
-#include <spot/twaalgos/emptiness.hh>
-
-namespace spot
-{
-
-  twa_run_ptr
-  project_twa_run(const const_twa_ptr& a_run,
-                   const const_twa_ptr& a_proj,
-                   const const_twa_run_ptr& run)
-  {
-    auto res = std::make_shared<twa_run>(a_proj);
-    for (auto& i: run->prefix)
-      res->prefix.emplace_back(a_run->project_state(i.s, a_proj),
-                               i.label, i.acc);
-    for (auto& i: run->cycle)
-      res->prefix.emplace_back(a_run->project_state(i.s, a_proj),
-                               i.label, i.acc);
-    return res;
-  }
-}
diff --git a/spot/twaalgos/projrun.hh b/spot/twaalgos/projrun.hh
deleted file mode 100644
index c0db25177..000000000
--- a/spot/twaalgos/projrun.hh
+++ /dev/null
@@ -1,48 +0,0 @@
-// -*- coding: utf-8 -*-
-// Copyright (C) 2013, 2014 Laboratoire de Recherche et Developpement
-// de l'Epita (LRDE).
-// Copyright (C) 2004  Laboratoire d'Informatique de Paris 6 (LIP6),
-// département Systèmes Répartis Coopératifs (SRC), Université Pierre
-// et Marie Curie.
-//
-// This file is part of Spot, a model checking library.
-//
-// Spot is free software; you can redistribute it and/or modify it
-// under the terms of the GNU General Public License as published by
-// the Free Software Foundation; either version 3 of the License, or
-// (at your option) any later version.
-//
-// Spot is distributed in the hope that it will be useful, but WITHOUT
-// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
-// or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
-// License for more details.
-//
-// You should have received a copy of the GNU General Public License
-// along with this program.  If not, see <http://www.gnu.org/licenses/>.
-
-#pragma once
-
-#include <spot/misc/common.hh>
-#include <iosfwd>
-#include <spot/twa/fwd.hh>
-#include <spot/twaalgos/emptiness.hh>
-
-namespace spot
-{
-  struct twa_run;
-
-  /// \ingroup twa_run
-  /// \brief Project a twa_run on a tgba.
-  ///
-  /// If a twa_run has been generated on a product, or any other
-  /// on-the-fly algorithm with tgba operands,
-  ///
-  /// \param run the run to replay
-  /// \param a_run the automata on which the run was generated
-  /// \param a_proj the automata on which to project the run
-  /// \return true iff the run could be completed
-  SPOT_API twa_run_ptr
-  project_twa_run(const const_twa_ptr& a_run,
-                   const const_twa_ptr& a_proj,
-                   const const_twa_run_ptr& run);
-}