diff --git a/build.sbt b/build.sbt
index 726bde9..fcd6f48 100644
--- a/build.sbt
+++ b/build.sbt
@@ -96,7 +96,10 @@ lazy val root = tlCrossRootProject
   .settings(name := projectName)
 
 val codeGen = Def.task {
-  val cache    = streams.value.cacheDirectory / "idna4s-codegen"
+  val cache =
+    streams.value.cacheDirectory / "idna4s-codegen" / thisProjectRef
+      .value
+      .project / scalaVersion.value
   val log      = streams.value.log
   val inputDir = cache / "inputs"
   IO.createDirectory(inputDir)