diff --git a/as/ast.c b/as/ast.c
index bfd6983..73b0314 100644
--- a/as/ast.c
+++ b/as/ast.c
@@ -1,4 +1,22 @@
-
+/* ast.c
+ *
+ *   Copyright (C) 2018   Henrik Hautakoski <henrik.hautakoski@gmail.com>
+ *
+ *   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 Street, Fifth Floor, Boston,
+ *   MA 02110-1301, USA.
+ */
 #include <string.h>
 #include <stdlib.h>
 #include <vector.h>
diff --git a/as/lexer.c b/as/lexer.c
index fb9db99..3046537 100644
--- a/as/lexer.c
+++ b/as/lexer.c
@@ -1,4 +1,22 @@
-
+/* lexer.c
+ *
+ *   Copyright (C) 2018   Henrik Hautakoski <henrik@fiktivkod.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 Street, Fifth Floor, Boston,
+ *   MA 02110-1301, USA.
+ */
 #include <stdio.h>
 #include <string.h>
 #include "asm_error.h"
diff --git a/vm/program.c b/vm/program.c
index 975f5c0..aa8e62a 100644
--- a/vm/program.c
+++ b/vm/program.c
@@ -1,4 +1,22 @@
-
+/* program.c
+ *
+ *   Copyright (C) 2012,2014   Henrik Hautakoski <henrik.hautakoski@gmail.com>
+ *
+ *   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 Street, Fifth Floor, Boston,
+ *   MA 02110-1301, USA.
+ */
 #include <string.h>
 #include <stdlib.h>
 #include <stdio.h>
diff --git a/vm/syscall.c b/vm/syscall.c
index 0378772..edbdeda 100644
--- a/vm/syscall.c
+++ b/vm/syscall.c
@@ -1,4 +1,4 @@
-/* syscall.h
+/* syscall.c
 *
 *   Copyright (C) 2012,2014-2015   Henrik Hautakoski <henrik.hautakoski@gmail.com>
 *