diff --git a/spot/ltsmin/Makefile.am b/spot/ltsmin/Makefile.am
index 7fe1862c6..b865bada5 100644
--- a/spot/ltsmin/Makefile.am
+++ b/spot/ltsmin/Makefile.am
@@ -39,7 +39,7 @@ libspotltsmin_la_LIBADD = \
   $(top_builddir)/lib/libgnu.la \
   $(LIBLTDL) -lpthread
 libspotltsmin_la_LDFLAGS = -no-undefined $(SYMBOLIC_LDFLAGS)
-libspotltsmin_la_SOURCES = ltsmin.cc spins_interface.cc
+libspotltsmin_la_SOURCES = ltsmin.cc
 
 
 EXTRA_DIST = $(srcdir)/libspotltsmin.pc.in
diff --git a/spot/ltsmin/spins_interface.cc b/spot/ltsmin/spins_interface.cc
deleted file mode 100644
index dbb1b8ec5..000000000
--- a/spot/ltsmin/spins_interface.cc
+++ /dev/null
@@ -1,32 +0,0 @@
-// -*- coding: utf-8 -*-
-// Copyright (C) 2017 Laboratoire de Recherche et Développement de
-// l'Epita (LRDE)
-//
-// 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/ltsmin/spins_interface.hh>
-#include <ltdl.h>
-
-namespace spot
-{
-  spins_interface::~spins_interface()
-  {
-    lt_dlhandle h = (lt_dlhandle) handle;
-    if (h)
-      lt_dlclose(h);
-    lt_dlexit();
-  }
-}
diff --git a/spot/ltsmin/spins_interface.hh b/spot/ltsmin/spins_interface.hh
index 15bfceb5d..0660f15f5 100644
--- a/spot/ltsmin/spins_interface.hh
+++ b/spot/ltsmin/spins_interface.hh
@@ -20,6 +20,7 @@
 #pragma once
 
 #include <memory>
+#include <ltdl.h>
 
 namespace spot
 {
@@ -51,7 +52,13 @@ namespace spot
     const char* (*get_type_name)(int type);
     int (*get_type_value_count)(int type);
     const char* (*get_type_value_name)(int type, int value);
-    ~spins_interface();
+    ~spins_interface()
+    {
+      lt_dlhandle h = (lt_dlhandle) handle;
+      if (h)
+        lt_dlclose(h);
+      lt_dlexit();
+    }
   };
 
   using spins_interface_ptr = std::shared_ptr<const spins_interface>;