diff --git a/go.mod b/go.mod
index 9685682..c30a1d3 100644
--- a/go.mod
+++ b/go.mod
@@ -4,6 +4,7 @@ go 1.13
 
 require (
 	github.com/go-redis/redis/v7 v7.4.0
+	github.com/golang/protobuf v1.4.1
 	github.com/google/go-cmp v0.5.0
 	github.com/google/uuid v1.2.0
 	github.com/robfig/cron/v3 v3.0.1
@@ -11,6 +12,6 @@ require (
 	go.uber.org/goleak v0.10.0
 	golang.org/x/sys v0.0.0-20191204072324-ce4227a45e2e
 	golang.org/x/time v0.0.0-20190308202827-9d24e82272b4
-	google.golang.org/protobuf v1.25.0 // indirect
+	google.golang.org/protobuf v1.25.0
 	gopkg.in/yaml.v2 v2.2.7 // indirect
 )
diff --git a/go.sum b/go.sum
index fd59ec7..dad6de7 100644
--- a/go.sum
+++ b/go.sum
@@ -22,12 +22,14 @@ github.com/golang/protobuf v1.4.0-rc.1.0.20200221234624-67d41d38c208/go.mod h1:x
 github.com/golang/protobuf v1.4.0-rc.2/go.mod h1:LlEzMj4AhA7rCAGe4KMBDvJI+AwstrUpVNzEA03Pprs=
 github.com/golang/protobuf v1.4.0-rc.4.0.20200313231945-b860323f09d0/go.mod h1:WU3c8KckQ9AFe+yFwt9sWVRKCVIyN9cPHBJSNnbL67w=
 github.com/golang/protobuf v1.4.0/go.mod h1:jodUvKwWbYaEsadDk5Fwe5c77LiNKVO9IDvqG2KuDX0=
+github.com/golang/protobuf v1.4.1 h1:ZFgWrT+bLgsYPirOnRfKLYJLvssAegOj/hgyMFdJZe0=
 github.com/golang/protobuf v1.4.1/go.mod h1:U8fpvMrcmy5pZrNK1lt4xCsGvpyWQ/VVv6QDs8UjoX8=
 github.com/google/go-cmp v0.2.0/go.mod h1:oXzfMopK8JAjlY9xF4vHSVASa0yLyX7SntLO5aqRK0M=
 github.com/google/go-cmp v0.3.0/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
 github.com/google/go-cmp v0.3.1/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
 github.com/google/go-cmp v0.4.0 h1:xsAVV57WRhGj6kEIi8ReJzQlHHqcBYCElAvkovg3B/4=
 github.com/google/go-cmp v0.4.0/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
+github.com/google/go-cmp v0.5.0 h1:/QaMHBdZ26BB3SSst0Iwl10Epc+xhTquomWX0oZEB6w=
 github.com/google/go-cmp v0.5.0/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/google/uuid v1.1.1 h1:Gkbcsh/GbpXz7lPftLA3P6TYMwjCLYm83jiFQZF/3gY=
 github.com/google/uuid v1.1.1/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
diff --git a/internal/asynqtest/asynqtest.go b/internal/asynqtest/asynqtest.go
index 8ee0193..f9d6aaa 100644
--- a/internal/asynqtest/asynqtest.go
+++ b/internal/asynqtest/asynqtest.go
@@ -6,7 +6,6 @@
 package asynqtest
 
 import (
-	"encoding/json"
 	"math"
 	"sort"
 	"testing"
@@ -130,7 +129,7 @@ func TaskMessageWithError(t base.TaskMessage, errMsg string) *base.TaskMessage {
 // Calling test will fail if marshaling errors out.
 func MustMarshal(tb testing.TB, msg *base.TaskMessage) string {
 	tb.Helper()
-	data, err := json.Marshal(msg)
+	data, err := base.EncodeMessage(msg)
 	if err != nil {
 		tb.Fatal(err)
 	}
@@ -141,12 +140,11 @@ func MustMarshal(tb testing.TB, msg *base.TaskMessage) string {
 // Calling test will fail if unmarshaling errors out.
 func MustUnmarshal(tb testing.TB, data string) *base.TaskMessage {
 	tb.Helper()
-	var msg base.TaskMessage
-	err := json.Unmarshal([]byte(data), &msg)
+	msg, err := base.DecodeMessage(data)
 	if err != nil {
 		tb.Fatal(err)
 	}
-	return &msg
+	return msg
 }
 
 // MustMarshalSlice marshals a slice of task messages and return a slice of
diff --git a/internal/base/base.go b/internal/base/base.go
index e412256..f30416b 100644
--- a/internal/base/base.go
+++ b/internal/base/base.go
@@ -6,6 +6,7 @@
 package base
 
 import (
+	"bytes"
 	"context"
 	"encoding/json"
 	"fmt"
@@ -16,6 +17,8 @@ import (
 
 	"github.com/go-redis/redis/v7"
 	"github.com/google/uuid"
+	pb "github.com/hibiken/asynq/internal/proto"
+	"google.golang.org/protobuf/proto"
 )
 
 // Version of asynq library and CLI.
@@ -195,8 +198,25 @@ type TaskMessage struct {
 }
 
 // EncodeMessage marshals the given task message in JSON and returns an encoded string.
+// TODO: Should return []byte instead of string
 func EncodeMessage(msg *TaskMessage) (string, error) {
-	b, err := json.Marshal(msg)
+	payload, err := json.Marshal(msg.Payload)
+	if err != nil {
+		return "", err
+	}
+	pbmsg := pb.TaskMessage{
+		Type:      msg.Type,
+		Payload:   payload,
+		Id:        msg.ID.String(),
+		Queue:     msg.Queue,
+		Retry:     int32(msg.Retry),
+		Retried:   int32(msg.Retried),
+		ErrorMsg:  msg.ErrorMsg,
+		Timeout:   msg.Timeout,
+		Deadline:  msg.Deadline,
+		UniqueKey: msg.UniqueKey,
+	}
+	b, err := proto.Marshal(&pbmsg)
 	if err != nil {
 		return "", err
 	}
@@ -204,14 +224,30 @@ func EncodeMessage(msg *TaskMessage) (string, error) {
 }
 
 // DecodeMessage unmarshals the given encoded string and returns a decoded task message.
+// TODO: should take []byte instead of string
 func DecodeMessage(s string) (*TaskMessage, error) {
-	d := json.NewDecoder(strings.NewReader(s))
-	d.UseNumber()
-	var msg TaskMessage
-	if err := d.Decode(&msg); err != nil {
+	var pbmsg pb.TaskMessage
+	if err := proto.Unmarshal([]byte(s), &pbmsg); err != nil {
 		return nil, err
 	}
-	return &msg, nil
+	d := json.NewDecoder(bytes.NewReader(pbmsg.Payload))
+	d.UseNumber()
+	payload := make(map[string]interface{})
+	if err := d.Decode(&payload); err != nil {
+		return nil, err
+	}
+	return &TaskMessage{
+		Type:      pbmsg.Type,
+		Payload:   payload,
+		ID:        uuid.MustParse(pbmsg.Id),
+		Queue:     pbmsg.Queue,
+		Retry:     int(pbmsg.Retry),
+		Retried:   int(pbmsg.Retried),
+		ErrorMsg:  pbmsg.ErrorMsg,
+		Timeout:   pbmsg.Timeout,
+		Deadline:  pbmsg.Deadline,
+		UniqueKey: pbmsg.UniqueKey,
+	}, nil
 }
 
 // Z represents sorted set member.
diff --git a/internal/proto/asynq.pb.go b/internal/proto/asynq.pb.go
index 57fb98a..373b32b 100644
--- a/internal/proto/asynq.pb.go
+++ b/internal/proto/asynq.pb.go
@@ -34,8 +34,8 @@ type TaskMessage struct {
 	Payload   []byte `protobuf:"bytes,2,opt,name=payload,proto3" json:"payload,omitempty"`
 	Id        string `protobuf:"bytes,3,opt,name=id,proto3" json:"id,omitempty"`
 	Queue     string `protobuf:"bytes,4,opt,name=queue,proto3" json:"queue,omitempty"`
-	Retry     string `protobuf:"bytes,5,opt,name=retry,proto3" json:"retry,omitempty"`
-	Retried   string `protobuf:"bytes,6,opt,name=retried,proto3" json:"retried,omitempty"`
+	Retry     int32  `protobuf:"varint,5,opt,name=retry,proto3" json:"retry,omitempty"`
+	Retried   int32  `protobuf:"varint,6,opt,name=retried,proto3" json:"retried,omitempty"`
 	ErrorMsg  string `protobuf:"bytes,7,opt,name=error_msg,json=errorMsg,proto3" json:"error_msg,omitempty"`
 	Timeout   int64  `protobuf:"varint,8,opt,name=timeout,proto3" json:"timeout,omitempty"`
 	Deadline  int64  `protobuf:"varint,9,opt,name=deadline,proto3" json:"deadline,omitempty"`
@@ -102,18 +102,18 @@ func (x *TaskMessage) GetQueue() string {
 	return ""
 }
 
-func (x *TaskMessage) GetRetry() string {
+func (x *TaskMessage) GetRetry() int32 {
 	if x != nil {
 		return x.Retry
 	}
-	return ""
+	return 0
 }
 
-func (x *TaskMessage) GetRetried() string {
+func (x *TaskMessage) GetRetried() int32 {
 	if x != nil {
 		return x.Retried
 	}
-	return ""
+	return 0
 }
 
 func (x *TaskMessage) GetErrorMsg() string {
@@ -155,9 +155,9 @@ var file_asynq_proto_rawDesc = []byte{
 	0x79, 0x6c, 0x6f, 0x61, 0x64, 0x12, 0x0e, 0x0a, 0x02, 0x69, 0x64, 0x18, 0x03, 0x20, 0x01, 0x28,
 	0x09, 0x52, 0x02, 0x69, 0x64, 0x12, 0x14, 0x0a, 0x05, 0x71, 0x75, 0x65, 0x75, 0x65, 0x18, 0x04,
 	0x20, 0x01, 0x28, 0x09, 0x52, 0x05, 0x71, 0x75, 0x65, 0x75, 0x65, 0x12, 0x14, 0x0a, 0x05, 0x72,
-	0x65, 0x74, 0x72, 0x79, 0x18, 0x05, 0x20, 0x01, 0x28, 0x09, 0x52, 0x05, 0x72, 0x65, 0x74, 0x72,
+	0x65, 0x74, 0x72, 0x79, 0x18, 0x05, 0x20, 0x01, 0x28, 0x05, 0x52, 0x05, 0x72, 0x65, 0x74, 0x72,
 	0x79, 0x12, 0x18, 0x0a, 0x07, 0x72, 0x65, 0x74, 0x72, 0x69, 0x65, 0x64, 0x18, 0x06, 0x20, 0x01,
-	0x28, 0x09, 0x52, 0x07, 0x72, 0x65, 0x74, 0x72, 0x69, 0x65, 0x64, 0x12, 0x1b, 0x0a, 0x09, 0x65,
+	0x28, 0x05, 0x52, 0x07, 0x72, 0x65, 0x74, 0x72, 0x69, 0x65, 0x64, 0x12, 0x1b, 0x0a, 0x09, 0x65,
 	0x72, 0x72, 0x6f, 0x72, 0x5f, 0x6d, 0x73, 0x67, 0x18, 0x07, 0x20, 0x01, 0x28, 0x09, 0x52, 0x08,
 	0x65, 0x72, 0x72, 0x6f, 0x72, 0x4d, 0x73, 0x67, 0x12, 0x18, 0x0a, 0x07, 0x74, 0x69, 0x6d, 0x65,
 	0x6f, 0x75, 0x74, 0x18, 0x08, 0x20, 0x01, 0x28, 0x03, 0x52, 0x07, 0x74, 0x69, 0x6d, 0x65, 0x6f,
diff --git a/internal/proto/asynq.proto b/internal/proto/asynq.proto
index cfe3a9b..0c6edf7 100644
--- a/internal/proto/asynq.proto
+++ b/internal/proto/asynq.proto
@@ -14,9 +14,9 @@ message TaskMessage {
 
   string queue = 4;
 
-  string retry = 5;
+  int32 retry = 5;
 
-  string retried = 6;
+  int32 retried = 6;
 
   string error_msg = 7;
 
diff --git a/internal/rdb/rdb_test.go b/internal/rdb/rdb_test.go
index 780cc56..0f4bcfd 100644
--- a/internal/rdb/rdb_test.go
+++ b/internal/rdb/rdb_test.go
@@ -101,7 +101,7 @@ func TestEnqueueUnique(t *testing.T) {
 	m1 := base.TaskMessage{
 		ID:        uuid.New(),
 		Type:      "email",
-		Payload:   map[string]interface{}{"user_id": float64(123)},
+		Payload:   map[string]interface{}{"user_id": json.Number("123")},
 		Queue:     base.DefaultQueueName,
 		UniqueKey: base.UniqueKey(base.DefaultQueueName, "email", map[string]interface{}{"user_id": 123}),
 	}