diff --git a/lib/vin_decoder.dart b/lib/vin_decoder.dart
index 08f0c05..a596681 100644
--- a/lib/vin_decoder.dart
+++ b/lib/vin_decoder.dart
@@ -1,5 +1,5 @@
 /// Support for VIN parsing, validation, and generation.
-// @dart=2.9
+// @dart=2.1
 
 library vin_decoder;