diff --git a/plugins/client.go b/plugins/client.go
index 791fb7f..973858c 100644
--- a/plugins/client.go
+++ b/plugins/client.go
@@ -15,10 +15,19 @@ import (
 )
 
 const (
-	versionMimetype = "application/vnd.docker.plugins.v1+json"
+	versionMimetype = "application/vnd.docker.plugins.v1.1+json"
 	defaultTimeOut  = 30
 )
 
+type remoteError struct {
+	method string
+	err    string
+}
+
+func (e *remoteError) Error() string {
+	return fmt.Sprintf("Plugin Error: %s, %s", e.err, e.method)
+}
+
 // NewClient creates a new plugin client (http).
 func NewClient(addr string, tlsConfig tlsconfig.Options) (*Client, error) {
 	tr := &http.Transport{}
@@ -84,9 +93,9 @@ func (c *Client) callWithRetry(serviceMethod string, args interface{}, ret inter
 		if resp.StatusCode != http.StatusOK {
 			remoteErr, err := ioutil.ReadAll(resp.Body)
 			if err != nil {
-				return fmt.Errorf("Plugin Error: %s", err)
+				return &remoteError{err.Error(), serviceMethod}
 			}
-			return fmt.Errorf("Plugin Error: %s", remoteErr)
+			return &remoteError{string(remoteErr), serviceMethod}
 		}
 
 		return json.NewDecoder(resp.Body).Decode(&ret)
diff --git a/plugins/pluginrpc-gen/parser.go b/plugins/pluginrpc-gen/parser.go
index b9746f8..b84fef0 100644
--- a/plugins/pluginrpc-gen/parser.go
+++ b/plugins/pluginrpc-gen/parser.go
@@ -7,7 +7,6 @@ import (
 	"go/parser"
 	"go/token"
 	"reflect"
-	"strings"
 )
 
 var ErrBadReturn = errors.New("found return arg with no name: all args must be named")
@@ -39,7 +38,7 @@ type arg struct {
 }
 
 func (a *arg) String() string {
-	return strings.ToLower(a.Name) + " " + strings.ToLower(a.ArgType)
+	return a.Name + " " + a.ArgType
 }
 
 // Parses the given file for an interface definition with the given name