diff --git a/README.md b/README.md
index 014dc95..03f63b5 100644
--- a/README.md
+++ b/README.md
@@ -18,7 +18,7 @@ addSbtPlugin("org.wvlet.airframe" % "sbt-airframe" % "(version)")
 
 To generate HTTP clients, add `airframeHttpClients` setting to your `build.sbt`. You need to specify
 which API package to use for generating RPC clients. The format
-is `<RPC package name>:<client type>(:<target package name>)?`. For example:
+is `<RPC package name>:<client type>(:<target package name>(.<target class name>)?)?`. For example:
 
 __build.sbt__
 
@@ -37,7 +37,7 @@ Supported client types are:
 - __async__: Create an async HTTP client (ServiceClient) for Scala (JVM) using Future
   abstraction (`F`). The `F` can be `scala.concurrent.Future` or twitter-util's Future.
 - __scalajs__:  Create an RPC client (ServiceClientJS)
-- __grpc__: Create gRPC client stubs (ServiceGrpc: SyncClient, AsyncClient)
+- __grpc__: Create gRPC client factory (ServiceGrpc: SyncClient, AsyncClient)
 
 To support other types of clients, see the examples
 of [HTTP code generators](https://github.com/wvlet/airframe/blob/master/airframe-http-codegen/src/main/scala/wvlet/airframe/http/codegen/client/ScalaHttpClientGenerator.scala)
diff --git a/build.sbt b/build.sbt
index 7e0cbb2..6dbcfba 100644
--- a/build.sbt
+++ b/build.sbt
@@ -1,8 +1,8 @@
 // Reload build.sbt on changes
 Global / onChangedBuildSource := ReloadOnSourceChanges
 
-val AIRFRAME_VERSION = sys.env.getOrElse("AIRFRAME_VERSION", "21.8.1")
-val AIRSPEC_VERSION  = "21.8.1"
+val AIRFRAME_VERSION = sys.env.getOrElse("AIRFRAME_VERSION", "21.9.0")
+val AIRSPEC_VERSION  = "21.9.0"
 val SCALA_2_12       = "2.12.14"
 
 ThisBuild / organization := "org.wvlet.airframe"