diff --git a/build.mill b/build.mill
index b5884e2..08b972a 100644
--- a/build.mill
+++ b/build.mill
@@ -10,7 +10,7 @@ import com.github.lolgab.mill.mima._
 val dottyCommunityBuildVersion = sys.props.get("dottyVersion").toList
 
 val scalaVersions =
-  "2.12.16" :: "2.13.8" :: "3.3.3" :: dottyCommunityBuildVersion
+  "2.12.21" :: "2.13.8" :: "3.3.3" :: dottyCommunityBuildVersion
 
 trait MimaCheck extends Mima {
   def mimaPreviousVersions = Seq("0.2.4", "0.2.5", "0.2.6", "0.2.7", "0.2.8", "0.3.0", "0.3.1")