Update copyright year 2019 --> 2020.
diff --git a/src/lex.c b/src/lex.c
index 281a176..98e2c62 100644
--- a/src/lex.c
+++ b/src/lex.c
@@ -1,7 +1,7 @@
 /*
  * *****************************************************************************
  *
- * Copyright (c) 2018-2019 Gavin D. Howard and contributors.
+ * Copyright (c) 2018-2020 Gavin D. Howard and contributors.
  *
  * All rights reserved.
  *