diff --git a/gdbus/client.c b/gdbus/client.c
index 84e0769..3b7faa4 100644
--- a/gdbus/client.c
+++ b/gdbus/client.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  *
  *  D-Bus helper library
@@ -5,20 +6,6 @@
  *  Copyright (C) 2004-2011  Marcel Holtmann <marcel@holtmann.org>
  *
  *
- *  This program 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 2 of the License, or
- *  (at your option) any later version.
- *
- *  This program 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, write to the Free Software
- *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
- *
  */
 
 #ifdef HAVE_CONFIG_H
diff --git a/gdbus/gdbus.h b/gdbus/gdbus.h
index 9bdff9e..28b8022 100644
--- a/gdbus/gdbus.h
+++ b/gdbus/gdbus.h
@@ -1,3 +1,4 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
 /*
  *
  *  D-Bus helper library
@@ -5,20 +6,6 @@
  *  Copyright (C) 2004-2011  Marcel Holtmann <marcel@holtmann.org>
  *
  *
- *  This program 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 2 of the License, or
- *  (at your option) any later version.
- *
- *  This program 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, write to the Free Software
- *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
- *
  */
 
 #ifndef __GDBUS_H
diff --git a/gdbus/mainloop.c b/gdbus/mainloop.c
index b90a844..a04ebb1 100644
--- a/gdbus/mainloop.c
+++ b/gdbus/mainloop.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  *
  *  D-Bus helper library
@@ -5,20 +6,6 @@
  *  Copyright (C) 2004-2011  Marcel Holtmann <marcel@holtmann.org>
  *
  *
- *  This program 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 2 of the License, or
- *  (at your option) any later version.
- *
- *  This program 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, write to the Free Software
- *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
- *
  */
 
 #ifdef HAVE_CONFIG_H
diff --git a/gdbus/object.c b/gdbus/object.c
index 49b5780..50a8b4f 100644
--- a/gdbus/object.c
+++ b/gdbus/object.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  *
  *  D-Bus helper library
@@ -5,20 +6,6 @@
  *  Copyright (C) 2004-2011  Marcel Holtmann <marcel@holtmann.org>
  *
  *
- *  This program 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 2 of the License, or
- *  (at your option) any later version.
- *
- *  This program 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, write to the Free Software
- *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
- *
  */
 
 #ifdef HAVE_CONFIG_H
diff --git a/gdbus/polkit.c b/gdbus/polkit.c
index 9e95fa3..80e024f 100644
--- a/gdbus/polkit.c
+++ b/gdbus/polkit.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  *
  *  D-Bus helper library
@@ -5,20 +6,6 @@
  *  Copyright (C) 2004-2011  Marcel Holtmann <marcel@holtmann.org>
  *
  *
- *  This program 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 2 of the License, or
- *  (at your option) any later version.
- *
- *  This program 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, write to the Free Software
- *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
- *
  */
 
 #ifdef HAVE_CONFIG_H
diff --git a/gdbus/watch.c b/gdbus/watch.c
index 447e486..25f3676 100644
--- a/gdbus/watch.c
+++ b/gdbus/watch.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
 /*
  *
  *  D-Bus helper library
@@ -5,20 +6,6 @@
  *  Copyright (C) 2004-2011  Marcel Holtmann <marcel@holtmann.org>
  *
  *
- *  This program 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 2 of the License, or
- *  (at your option) any later version.
- *
- *  This program 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, write to the Free Software
- *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
- *
  */
 
 #ifdef HAVE_CONFIG_H