diff --git a/spot/ltsmin/Makefile.am b/spot/ltsmin/Makefile.am
index b865bada5..7fe1862c6 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
+libspotltsmin_la_SOURCES = ltsmin.cc spins_interface.cc
 
 
 EXTRA_DIST = $(srcdir)/libspotltsmin.pc.in
diff --git a/spot/ltsmin/spins_interface.cc b/spot/ltsmin/spins_interface.cc
new file mode 100644
index 000000000..dbb1b8ec5
--- /dev/null
+++ b/spot/ltsmin/spins_interface.cc
@@ -0,0 +1,32 @@
+// -*- 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 f77f87aca..15bfceb5d 100644
--- a/spot/ltsmin/spins_interface.hh
+++ b/spot/ltsmin/spins_interface.hh
@@ -19,8 +19,8 @@
 
 #pragma once
 
-#include <ltdl.h>
 #include <memory>
+
 namespace spot
 {
   ////////////////////////////////////////////////////////////////////////
@@ -38,7 +38,9 @@ namespace spot
 
   struct spins_interface
   {
-    lt_dlhandle handle;        // handle to the dynamic library
+    // handle to the dynamic library. The variable is of type lt_dlhandle, but
+    // we need this trick since we cannot put ltdl.h in public headers
+    void* handle;
     void (*get_initial_state)(void *to);
     int (*have_property)();
     int (*get_successors)(void* m, int *in, TransitionCB, void *arg);
@@ -49,13 +51,7 @@ 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()
-    {
-      if (handle)
-        lt_dlclose(handle);
-      lt_dlexit();
-    }
+    ~spins_interface();
   };
 
   using spins_interface_ptr = std::shared_ptr<const spins_interface>;