diff --git a/play-ahc-ws-standalone/src/main/scala/play/api/libs/ws/ahc/FormUrlEncodedParser.scala b/play-ahc-ws-standalone/src/main/scala/play/api/libs/ws/ahc/FormUrlEncodedParser.scala
index 44303b96..33eca1c5 100644
--- a/play-ahc-ws-standalone/src/main/scala/play/api/libs/ws/ahc/FormUrlEncodedParser.scala
+++ b/play-ahc-ws-standalone/src/main/scala/play/api/libs/ws/ahc/FormUrlEncodedParser.scala
@@ -15,7 +15,8 @@ private[ahc] object FormUrlEncodedParser {
    */
   def parseNotPreservingOrder(data: String, encoding: String = "utf-8"): Map[String, Seq[String]] = {
     // Generate the pairs of values from the string.
-    parseToPairs(data, encoding).groupBy(_._1).map(param => param._1 -> param._2.map(_._2)).toMap
+    parseToPairs(data, encoding).groupBy(_._1).
+      map(param => param._1 -> param._2.map(_._2))(scala.collection.breakOut)
   }
 
   /**