diff --git a/protocol/src/main/scala/sbt/internal/protocol/codec/JsonRpcRequestMessageFormats.scala b/protocol/src/main/scala/sbt/internal/protocol/codec/JsonRpcRequestMessageFormats.scala
index dac0987e4..2c1273534 100644
--- a/protocol/src/main/scala/sbt/internal/protocol/codec/JsonRpcRequestMessageFormats.scala
+++ b/protocol/src/main/scala/sbt/internal/protocol/codec/JsonRpcRequestMessageFormats.scala
@@ -24,7 +24,10 @@ trait JsonRpcRequestMessageFormats {
             val id = try {
               unbuilder.readField[String]("id")
             } catch {
-              case _: Throwable => unbuilder.readField[Long]("id").toString
+              case _: Throwable => {
+                val prefix = "\u2668" // Append prefix to show the original type was Number
+                prefix + unbuilder.readField[Long]("id").toString
+              }
             }
             val method = unbuilder.readField[String]("method")
             val params = unbuilder.lookupField("params") map {
diff --git a/protocol/src/main/scala/sbt/internal/protocol/codec/JsonRpcResponseMessageFormats.scala b/protocol/src/main/scala/sbt/internal/protocol/codec/JsonRpcResponseMessageFormats.scala
index d10164e67..c9d943296 100644
--- a/protocol/src/main/scala/sbt/internal/protocol/codec/JsonRpcResponseMessageFormats.scala
+++ b/protocol/src/main/scala/sbt/internal/protocol/codec/JsonRpcResponseMessageFormats.scala
@@ -7,8 +7,8 @@
 
 package sbt.internal.protocol.codec
 
-import _root_.sjsonnew.{ Unbuilder, Builder, JsonFormat, deserializationError }
-import sjsonnew.shaded.scalajson.ast.unsafe.JValue
+import _root_.sjsonnew.{ Builder, JsonFormat, Unbuilder, deserializationError }
+import sjsonnew.shaded.scalajson.ast.unsafe._
 
 trait JsonRpcResponseMessageFormats {
   self: sbt.internal.util.codec.JValueFormats
@@ -45,10 +45,35 @@ trait JsonRpcResponseMessageFormats {
       }
       override def write[J](obj: sbt.internal.protocol.JsonRpcResponseMessage,
                             builder: Builder[J]): Unit = {
+        // Parse given id to Long or String judging by prefix
+        def parseId(str: String): Either[Long, String] = {
+          if (str.startsWith("\u2668")) Left(str.substring(1).toLong)
+          else Right(str)
+        }
+        def parseResult(jValue: JValue): JValue = jValue match {
+          case JObject(jFields) =>
+            val replaced = jFields map {
+              case field @ JField("execId", JString(str)) =>
+                parseId(str) match {
+                  case Right(strId) => field.copy(value = JString(strId))
+                  case Left(longId) => field.copy(value = JNumber(longId))
+                }
+              case other =>
+                other
+            }
+            JObject(replaced)
+          case other =>
+            other
+        }
         builder.beginObject()
         builder.addField("jsonrpc", obj.jsonrpc)
-        builder.addField("id", obj.id)
-        builder.addField("result", obj.result)
+        obj.id foreach { id =>
+          parseId(id) match {
+            case Right(strId) => builder.addField("id", strId)
+            case Left(longId) => builder.addField("id", longId)
+          }
+        }
+        builder.addField("result", obj.result map parseResult)
         builder.addField("error", obj.error)
         builder.endObject()
       }
diff --git a/sbt/src/test/scala/sbt/ServerSpec.scala b/sbt/src/test/scala/sbt/ServerSpec.scala
index 7ad307fd8..a328c6dfe 100644
--- a/sbt/src/test/scala/sbt/ServerSpec.scala
+++ b/sbt/src/test/scala/sbt/ServerSpec.scala
@@ -9,6 +9,7 @@ package sbt
 
 import org.scalatest._
 import scala.concurrent._
+import scala.annotation.tailrec
 import java.io.{ InputStream, OutputStream }
 import java.util.concurrent.atomic.AtomicInteger
 import java.util.concurrent.{ ThreadFactory, ThreadPoolExecutor }
@@ -23,15 +24,22 @@ class ServerSpec extends AsyncFlatSpec with Matchers {
         """{ "jsonrpc": "2.0", "id": 3, "method": "sbt/setting", "params": { "setting": "root/name" } }""",
         out)
       Thread.sleep(100)
-      val l2 = contentLength(in)
-      println(l2)
-      readLine(in)
-      readLine(in)
-      val x2 = readContentLength(in, l2)
-      println(x2)
-      assert(1 == 1)
+      assert(waitFor(in, 10) { s =>
+        s contains """"id":3"""
+      })
     }
   }
+
+  @tailrec
+  private[this] def waitFor(in: InputStream, num: Int)(f: String => Boolean): Boolean = {
+    if (num < 0) false
+    else
+      readFrame(in) match {
+        case Some(x) if f(x) => true
+        case _ =>
+          waitFor(in, num - 1)(f)
+      }
+  }
 }
 
 object ServerSpec {
@@ -90,6 +98,13 @@ object ServerSpec {
     writeLine(message, out)
   }
 
+  def readFrame(in: InputStream): Option[String] = {
+    val l = contentLength(in)
+    readLine(in)
+    readLine(in)
+    readContentLength(in, l)
+  }
+
   def contentLength(in: InputStream): Int = {
     readLine(in) map { line =>
       line.drop(16).toInt