diff --git a/build.sbt b/build.sbt
index efe7307..0044b8d 100644
--- a/build.sbt
+++ b/build.sbt
@@ -4,7 +4,7 @@ val Scala213 = "2.13.18"
 val Scala3 = "3.3.7"
 
 ThisBuild / tlBaseVersion := "0.4"
-ThisBuild / crossScalaVersions := Seq("2.12.20", Scala213, Scala3)
+ThisBuild / crossScalaVersions := Seq("2.12.21", Scala213, Scala3)
 ThisBuild / tlVersionIntroduced := Map("3" -> "0.4.3")
 ThisBuild / developers += tlGitHubDev("ChristopherDavenport", "Christopher Davenport")
 ThisBuild / startYear := Some(2019)