diff --git a/build.sbt b/build.sbt
index f16d2c9..261934f 100644
--- a/build.sbt
+++ b/build.sbt
@@ -10,6 +10,14 @@ lazy val scalaOAuth2ProviderSettings =
       scalaVersion := "3.3.0",
       crossScalaVersions ++= Seq("2.13.12", "2.12.18", "2.11.12"),
       scalacOptions ++= Seq("-deprecation", "-unchecked", "-feature"),
+      scalacOptions ++= {
+        scalaBinaryVersion.value match {
+          case "2.12" | "2.13" =>
+            Seq("-Xsource:3")
+          case _ =>
+            Nil
+        }
+      },
       publishTo := {
         val v = version.value
         val nexus = "https://oss.sonatype.org/"
diff --git a/src/test/scala/scalaoauth2/provider/TokenEndPointSpec.scala b/src/test/scala/scalaoauth2/provider/TokenEndPointSpec.scala
index 9d50abc..427efeb 100644
--- a/src/test/scala/scalaoauth2/provider/TokenEndPointSpec.scala
+++ b/src/test/scala/scalaoauth2/provider/TokenEndPointSpec.scala
@@ -50,7 +50,8 @@ class TokenEndPointSpec extends AnyFlatSpec with ScalaFutures {
 
     val dataHandler = successfulDataHandler()
     val f = new TokenEndpoint {
-      override val handlers = Map("password" -> new Password())
+      override val handlers: Map[String, Password] =
+        Map("password" -> new Password())
     }.handleRequest(request, dataHandler)
 
     whenReady(f) { result =>
@@ -128,7 +129,8 @@ class TokenEndPointSpec extends AnyFlatSpec with ScalaFutures {
 
     val dataHandler = successfulDataHandler()
     val f = new TokenEndpoint {
-      override val handlers = Map("password" -> new Password())
+      override val handlers: Map[String, Password] =
+        Map("password" -> new Password())
     }.handleRequest(request, dataHandler)
 
     whenReady(f) { result =>
@@ -159,7 +161,8 @@ class TokenEndPointSpec extends AnyFlatSpec with ScalaFutures {
     }
 
     val f = new TokenEndpoint {
-      override val handlers = Map("password" -> passwordNoCred)
+      override val handlers: Map[String, Password] =
+        Map("password" -> passwordNoCred)
     }.handleRequest(request, dataHandler)
 
     whenReady(f) { result =>
@@ -192,7 +195,8 @@ class TokenEndPointSpec extends AnyFlatSpec with ScalaFutures {
     }
 
     val f = new TokenEndpoint {
-      override val handlers = Map("password" -> new Password())
+      override val handlers: Map[String, Password] =
+        Map("password" -> new Password())
     }.handleRequest(request, dataHandler)
 
     whenReady(f) { result =>
@@ -249,7 +253,8 @@ class TokenEndPointSpec extends AnyFlatSpec with ScalaFutures {
   it should "be possible to customize supporting grant types" in {
 
     object TestTokenEndpoint extends TokenEndpoint {
-      override val handlers = Map("password" -> new Password())
+      override val handlers: Map[String, Password] =
+        Map("password" -> new Password())
     }
 
     val f = TestTokenEndpoint.handleRequest(
@@ -296,7 +301,8 @@ class TokenEndPointSpec extends AnyFlatSpec with ScalaFutures {
     }
 
     val f = new TokenEndpoint {
-      override val handlers = Map("password" -> new Password())
+      override val handlers: Map[String, Password] =
+        Map("password" -> new Password())
     }.handleRequest(request, dataHandler)
 
     whenReady(f) { result =>
@@ -335,7 +341,8 @@ class TokenEndPointSpec extends AnyFlatSpec with ScalaFutures {
     }
 
     val f = new TokenEndpoint {
-      override val handlers = Map("password" -> new Password())
+      override val handlers: Map[String, Password] =
+        Map("password" -> new Password())
     }.handleRequest(request, dataHandler)
 
     whenReady(f) { result =>