diff --git a/akka-http-tests/src/test/scala/akka/http/scaladsl/server/directives/RangeDirectivesSpec.scala b/akka-http-tests/src/test/scala/akka/http/scaladsl/server/directives/RangeDirectivesSpec.scala
index dc678809ef..fb4aca5a37 100644
--- a/akka-http-tests/src/test/scala/akka/http/scaladsl/server/directives/RangeDirectivesSpec.scala
+++ b/akka-http-tests/src/test/scala/akka/http/scaladsl/server/directives/RangeDirectivesSpec.scala
@@ -78,13 +78,13 @@ class RangeDirectivesSpec extends RoutingSpec with Inspectors with Inside {
 
     "reject an unsatisfiable single range" in {
       Get() ~> addHeader(Range(ByteRange(100, 200))) ~> completeWithRangedBytes(10) ~> check {
-        rejection shouldEqual UnsatisfiableRangeRejection(Seq(ByteRange(100, 200)), 10)
+        rejection shouldEqual UnsatisfiableRangeRejection(ByteRange(100, 200) :: Nil, 10)
       }
     }
 
     "reject an unsatisfiable single suffix range with length 0" in {
       Get() ~> addHeader(Range(ByteRange.suffix(0))) ~> completeWithRangedBytes(42) ~> check {
-        rejection shouldEqual UnsatisfiableRangeRejection(Seq(ByteRange.suffix(0)), 42)
+        rejection shouldEqual UnsatisfiableRangeRejection(ByteRange.suffix(0) :: Nil, 42)
       }
     }
 
diff --git a/akka-http/src/main/scala/akka/http/scaladsl/server/Rejection.scala b/akka-http/src/main/scala/akka/http/scaladsl/server/Rejection.scala
index 95db843ece..44a3b5808f 100644
--- a/akka-http/src/main/scala/akka/http/scaladsl/server/Rejection.scala
+++ b/akka-http/src/main/scala/akka/http/scaladsl/server/Rejection.scala
@@ -70,7 +70,7 @@ case class MalformedHeaderRejection(headerName: String, errorMsg: String,
  * Rejection created by unmarshallers.
  * Signals that the request was rejected because the requests content-type is unsupported.
  */
-case class UnsupportedRequestContentTypeRejection(supported: Set[ContentTypeRange]) extends Rejection
+case class UnsupportedRequestContentTypeRejection(supported: immutable.Set[ContentTypeRange]) extends Rejection
 
 /**
  * Rejection created by decoding filters.
@@ -83,7 +83,7 @@ case class UnsupportedRequestEncodingRejection(supported: HttpEncoding) extends
  * Signals that the request was rejected because the requests contains only unsatisfiable ByteRanges.
  * The actualEntityLength gives the client a hint to create satisfiable ByteRanges.
  */
-case class UnsatisfiableRangeRejection(unsatisfiableRanges: Seq[ByteRange], actualEntityLength: Long) extends Rejection
+case class UnsatisfiableRangeRejection(unsatisfiableRanges: immutable.Seq[ByteRange], actualEntityLength: Long) extends Rejection
 
 /**
  * Rejection created by range directives.
@@ -112,14 +112,14 @@ case object RequestEntityExpectedRejection extends Rejection
  * Signals that the request was rejected because the service is not capable of producing a response entity whose
  * content type is accepted by the client
  */
-case class UnacceptedResponseContentTypeRejection(supported: Set[ContentType]) extends Rejection
+case class UnacceptedResponseContentTypeRejection(supported: immutable.Set[ContentType]) extends Rejection
 
 /**
  * Rejection created by encoding filters.
  * Signals that the request was rejected because the service is not capable of producing a response entity whose
  * content encoding is accepted by the client
  */
-case class UnacceptedResponseEncodingRejection(supported: Set[HttpEncoding]) extends Rejection
+case class UnacceptedResponseEncodingRejection(supported: immutable.Set[HttpEncoding]) extends Rejection
 object UnacceptedResponseEncodingRejection {
   def apply(supported: HttpEncoding): UnacceptedResponseEncodingRejection = UnacceptedResponseEncodingRejection(Set(supported))
 }
diff --git a/akka-http/src/main/scala/akka/http/scaladsl/server/directives/RangeDirectives.scala b/akka-http/src/main/scala/akka/http/scaladsl/server/directives/RangeDirectives.scala
index 53aea321e4..09bca74261 100644
--- a/akka-http/src/main/scala/akka/http/scaladsl/server/directives/RangeDirectives.scala
+++ b/akka-http/src/main/scala/akka/http/scaladsl/server/directives/RangeDirectives.scala
@@ -97,7 +97,7 @@ trait RangeDirectives {
         case _                  ⇒ None
       }
 
-      def applyRanges(ranges: Seq[ByteRange]): Directive0 =
+      def applyRanges(ranges: immutable.Seq[ByteRange]): Directive0 =
         extractRequestContext.flatMap { ctx ⇒
           mapRouteResultWithPF {
             case Complete(HttpResponse(OK, headers, entity, protocol)) ⇒