diff --git a/grpc.go b/grpc.go
index f230fa4..ef0c9be 100644
--- a/grpc.go
+++ b/grpc.go
@@ -8,6 +8,7 @@ import (
 	"net"
 	"reflect"
 	"strings"
+	"sync"
 	"sync/atomic"
 	"time"
 
@@ -24,9 +25,11 @@ import (
 )
 
 type grpcClient struct {
-	opts client.Options
-	pool *pool
-	once atomic.Value
+	opts   client.Options
+	codecs map[string]encoding.Codec
+	pool   *pool
+	once   atomic.Value
+	sync.RWMutex
 }
 
 func init() {
@@ -301,18 +304,13 @@ func (g *grpcClient) maxSendMsgSizeValue() int {
 }
 
 func (g *grpcClient) newGRPCCodec(contentType string) (encoding.Codec, error) {
-	codecs := make(map[string]encoding.Codec)
-	if g.opts.Context != nil {
-		if v := g.opts.Context.Value(codecsKey{}); v != nil {
-			codecs = v.(map[string]encoding.Codec)
-		}
-	}
-	if c, ok := codecs[contentType]; ok {
-		return wrapCodec{c}, nil
-	}
-	if c, ok := defaultGRPCCodecs[contentType]; ok {
+	g.RLock()
+	defer g.RUnlock()
+
+	if c, ok := g.codecs[contentType]; ok {
 		return wrapCodec{c}, nil
 	}
+
 	return nil, fmt.Errorf("Unsupported Content-Type: %s", contentType)
 }
 
@@ -721,6 +719,22 @@ func newClient(opts ...client.Option) client.Client {
 		c = options.Wrappers[i-1](c)
 	}
 
+	rc.codecs = make(map[string]encoding.Codec, len(defaultGRPCCodecs))
+	for k, v := range defaultGRPCCodecs {
+		rc.codecs[k] = v
+	}
+
+	var codecs map[string]encoding.Codec
+	if rc.opts.Context != nil {
+		if v := rc.opts.Context.Value(codecsKey{}); v != nil {
+			codecs = v.(map[string]encoding.Codec)
+		}
+	}
+
+	for k, v := range codecs {
+		rc.codecs[k] = v
+	}
+
 	return c
 }