diff --git a/src/common.c b/src/common.c
index 3fa2d30..e25ff31 100644
--- a/src/common.c
+++ b/src/common.c
@@ -1,3 +1,10 @@
+/* Copyright (c), Niclas Meyer <niclas@countingsort.com>
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
 #include "common.h"
 
 #include <stdarg.h>
diff --git a/src/common.h b/src/common.h
index 83e4d47..3cf1ec8 100644
--- a/src/common.h
+++ b/src/common.h
@@ -1,3 +1,10 @@
+/* Copyright (c), Niclas Meyer <niclas@countingsort.com>
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
 #ifndef COMMON_H
 #define COMMON_H