Ensure that all classes are compiled with Java 11 bytecode

build.sbt

@@ -5,6 +5,7 @@ ThisBuild / organization := "com.velocidi"
 
 ThisBuild / crossScalaVersions := Seq("2.12.18", "2.13.12")
 ThisBuild / scalaVersion       := "2.13.12"
+val javaVersion                 = "11"
 
 // Workaround for incompatible scala-xml versions taken from https://github.com/scala/bug/issues/12632. scala-xml 1.x
 // and scala-xml 2.x are "mostly" binary compatible.
@@ -118,6 +119,7 @@ lazy val commonSettings = Seq(
       "-feature",
       "-unchecked",
       "-deprecation",
+      "-release", javaVersion,
       "-Xfatal-warnings",
       "-Ywarn-dead-code")
 
@@ -135,6 +137,10 @@ lazy val commonSettings = Seq(
     }
   },
 
+  javacOptions ++= List(
+    "--release", javaVersion
+  ),
+
   autoAPIMappings := true,
 
   publishTo := sonatypePublishToBundle.value,