diff --git a/command.go b/command.go
index 15a04c0e..0108f8ba 100644
--- a/command.go
+++ b/command.go
@@ -457,7 +457,7 @@ func (cmd *BoolCmd) readReply(cn *pool.Conn) error {
 type StringCmd struct {
 	baseCmd
 
-	val []byte
+	val string
 }
 
 func NewStringCmd(args ...interface{}) *StringCmd {
@@ -466,12 +466,12 @@ func NewStringCmd(args ...interface{}) *StringCmd {
 }
 
 func (cmd *StringCmd) reset() {
-	cmd.val = nil
+	cmd.val = ""
 	cmd.err = nil
 }
 
 func (cmd *StringCmd) Val() string {
-	return string(cmd.val)
+	return cmd.val
 }
 
 func (cmd *StringCmd) Result() (string, error) {
@@ -479,7 +479,7 @@ func (cmd *StringCmd) Result() (string, error) {
 }
 
 func (cmd *StringCmd) Bytes() ([]byte, error) {
-	return cmd.val, cmd.err
+	return []byte(cmd.val), cmd.err
 }
 
 func (cmd *StringCmd) Int64() (int64, error) {
@@ -520,11 +520,7 @@ func (cmd *StringCmd) readReply(cn *pool.Conn) error {
 		cmd.err = err
 		return err
 	}
-
-	new := make([]byte, len(b))
-	copy(new, b)
-	cmd.val = new
-
+	cmd.val = string(b)
 	return nil
 }
 
diff --git a/internal/proto/proto.go b/internal/proto/proto.go
index 1d975202..e1c1ed4a 100644
--- a/internal/proto/proto.go
+++ b/internal/proto/proto.go
@@ -8,97 +8,85 @@ import (
 	"gopkg.in/redis.v5/internal"
 )
 
-const (
-	ErrorReply  = '-'
-	StatusReply = '+'
-	IntReply    = ':'
-	StringReply = '$'
-	ArrayReply  = '*'
-)
-
-const defaultBufSize = 4096
-
-const errScanNil = internal.RedisError("redis: Scan(nil)")
-
-func Scan(b []byte, val interface{}) error {
+func Scan(s string, val interface{}) error {
 	switch v := val.(type) {
 	case nil:
-		return errScanNil
+		return internal.RedisError("redis: Scan(nil)")
 	case *string:
-		*v = string(b)
+		*v = s
 		return nil
 	case *[]byte:
-		*v = b
+		*v = []byte(s)
 		return nil
 	case *int:
 		var err error
-		*v, err = strconv.Atoi(string(b))
+		*v, err = strconv.Atoi(s)
 		return err
 	case *int8:
-		n, err := strconv.ParseInt(string(b), 10, 8)
+		n, err := strconv.ParseInt(s, 10, 8)
 		if err != nil {
 			return err
 		}
 		*v = int8(n)
 		return nil
 	case *int16:
-		n, err := strconv.ParseInt(string(b), 10, 16)
+		n, err := strconv.ParseInt(s, 10, 16)
 		if err != nil {
 			return err
 		}
 		*v = int16(n)
 		return nil
 	case *int32:
-		n, err := strconv.ParseInt(string(b), 10, 32)
+		n, err := strconv.ParseInt(s, 10, 32)
 		if err != nil {
 			return err
 		}
 		*v = int32(n)
 		return nil
 	case *int64:
-		n, err := strconv.ParseInt(string(b), 10, 64)
+		n, err := strconv.ParseInt(s, 10, 64)
 		if err != nil {
 			return err
 		}
 		*v = n
 		return nil
 	case *uint:
-		n, err := strconv.ParseUint(string(b), 10, 64)
+		n, err := strconv.ParseUint(s, 10, 64)
 		if err != nil {
 			return err
 		}
 		*v = uint(n)
 		return nil
 	case *uint8:
-		n, err := strconv.ParseUint(string(b), 10, 8)
+		n, err := strconv.ParseUint(s, 10, 8)
 		if err != nil {
 			return err
 		}
 		*v = uint8(n)
 		return nil
 	case *uint16:
-		n, err := strconv.ParseUint(string(b), 10, 16)
+		n, err := strconv.ParseUint(s, 10, 16)
 		if err != nil {
 			return err
 		}
 		*v = uint16(n)
 		return nil
 	case *uint32:
-		n, err := strconv.ParseUint(string(b), 10, 32)
+		n, err := strconv.ParseUint(s, 10, 32)
 		if err != nil {
 			return err
 		}
 		*v = uint32(n)
 		return nil
 	case *uint64:
-		n, err := strconv.ParseUint(string(b), 10, 64)
+		n, err := strconv.ParseUint(s, 10, 64)
 		if err != nil {
 			return err
 		}
 		*v = n
 		return nil
 	case *float32:
-		n, err := strconv.ParseFloat(string(b), 32)
+		n, err := strconv.ParseFloat(s, 32)
 		if err != nil {
 			return err
 		}
@@ -106,14 +94,14 @@ func Scan(b []byte, val interface{}) error {
 		return err
 	case *float64:
 		var err error
-		*v, err = strconv.ParseFloat(string(b), 64)
+		*v, err = strconv.ParseFloat(s, 64)
 		return err
 	case *bool:
-		*v = len(b) == 1 && b[0] == '1'
+		*v = len(s) == 1 && s[0] == '1'
 		return nil
 	default:
 		if bu, ok := val.(encoding.BinaryUnmarshaler); ok {
-			return bu.UnmarshalBinary(b)
+			return bu.UnmarshalBinary([]byte(s))
 		}
 		err := fmt.Errorf(
 			"redis: can't unmarshal %T (consider implementing BinaryUnmarshaler)", val)
diff --git a/internal/proto/reader.go b/internal/proto/reader.go
index bd76e3a8..7e728463 100644
--- a/internal/proto/reader.go
+++ b/internal/proto/reader.go
@@ -11,7 +11,13 @@ import (
 
 const bytesAllocLimit = 1024 * 1024 // 1mb
 
-const errEmptyReply = internal.RedisError("redis: reply is empty")
+const (
+	ErrorReply  = '-'
+	StatusReply = '+'
+	IntReply    = ':'
+	StringReply = '$'
+	ArrayReply  = '*'
+)
 
 type MultiBulkParse func(*Reader, int64) (interface{}, error)
 
@@ -23,7 +29,7 @@ type Reader struct {
 func NewReader(rd io.Reader) *Reader {
 	return &Reader{
 		src: bufio.NewReader(rd),
-		buf: make([]byte, 0, defaultBufSize),
+		buf: make([]byte, 0, bufferSize),
 	}
 }
 
@@ -48,7 +54,7 @@ func (p *Reader) ReadLine() ([]byte, error) {
 		return nil, bufio.ErrBufferFull
 	}
 	if len(line) == 0 {
-		return nil, errEmptyReply
+		return nil, internal.RedisError("redis: reply is empty")
 	}
 	if isNilReply(line) {
 		return nil, internal.Nil
diff --git a/internal/proto/writebuffer.go b/internal/proto/writebuffer.go
index 8164f7f2..1e0f8e6c 100644
--- a/internal/proto/writebuffer.go
+++ b/internal/proto/writebuffer.go
@@ -6,11 +6,13 @@ import (
 	"strconv"
 )
 
+const bufferSize = 4096
+
 type WriteBuffer struct{ b []byte }
 
 func NewWriteBuffer() *WriteBuffer {
 	return &WriteBuffer{
-		b: make([]byte, 0, defaultBufSize),
+		b: make([]byte, 0, bufferSize),
 	}
 }
 
diff --git a/result.go b/result.go
index 481673d2..f5c7084c 100644
--- a/result.go
+++ b/result.go
@@ -51,7 +51,7 @@ func NewBoolResult(val bool, err error) *BoolCmd {
 }
 
 // NewStringResult returns a StringCmd initalised with val and err for testing
-func NewStringResult(val []byte, err error) *StringCmd {
+func NewStringResult(val string, err error) *StringCmd {
 	var cmd StringCmd
 	cmd.val = val
 	cmd.setErr(err)