diff --git a/main/src/main/scala/sbt/Defaults.scala b/main/src/main/scala/sbt/Defaults.scala
index ef757c0d5..bcd4c68f3 100644
--- a/main/src/main/scala/sbt/Defaults.scala
+++ b/main/src/main/scala/sbt/Defaults.scala
@@ -1002,6 +1002,15 @@ object Defaults extends BuildCommon {
           )
         else Def.uncached(old)
       },
+      scalacOptions := {
+        val old = scalacOptions.value
+        if (
+          sbtPlugin.value && VersionNumber(scalaVersion.value)
+            .matchesSemVer(SemanticSelector("=2.12 >=2.12.13"))
+        )
+          old ++ Seq("-Wconf:cat=unused-nowarn:s", "-Xsource:3")
+        else old
+      },
       persistJarClasspath :== true,
       classpathEntryDefinesClassVF := Def.uncached {
         val cache =