diff --git a/middleware.go b/middleware.go
index 162342a5..e5c4eef7 100644
--- a/middleware.go
+++ b/middleware.go
@@ -192,9 +192,13 @@ func createHTTPRequest(c *Client, r *Request) (err error) {
 			r.RawRequest, err = http.NewRequest(r.Method, r.URL, nil)
 		}
 	} else {
-		// fix data race: must deep copy.
-		bodyBuf := bytes.NewBuffer(append([]byte{}, r.bodyBuf.Bytes()...))
-		r.RawRequest, err = http.NewRequest(r.Method, r.URL, bodyBuf)
+		// deep copy
+		bodyCopy := acquireBuffer()
+		_, err := io.Copy(bodyCopy, bytes.NewReader(r.bodyBuf.Bytes()))
+		if err != nil {
+			return err
+		}
+		r.RawRequest, err = http.NewRequest(r.Method, r.URL, bodyCopy)
 	}
 
 	if err != nil {
@@ -228,17 +232,18 @@ func createHTTPRequest(c *Client, r *Request) (err error) {
 		r.RawRequest = r.RawRequest.WithContext(r.ctx)
 	}
 
-	bodyCopy, err := getBodyCopy(r)
-	if err != nil {
-		return err
-	}
+	if r.bodyBuf == nil {
+		bodyCopy, err := getRawRequestBodyCopy(r)
+		if err != nil {
+			return err
+		}
 
-	// assign get body func for the underlying raw request instance
-	r.RawRequest.GetBody = func() (io.ReadCloser, error) {
 		if bodyCopy != nil {
-			return io.NopCloser(bytes.NewReader(bodyCopy.Bytes())), nil
+			// assign get body func for the underlying raw request instance
+			r.RawRequest.GetBody = func() (io.ReadCloser, error) {
+				return io.NopCloser(bytes.NewReader(bodyCopy.Bytes())), nil
+			}
 		}
-		return nil, nil
 	}
 
 	return
@@ -544,17 +549,7 @@ func saveResponseIntoFile(c *Client, res *Response) error {
 	return nil
 }
 
-func getBodyCopy(r *Request) (*bytes.Buffer, error) {
-	// If r.bodyBuf present, return the copy
-	if r.bodyBuf != nil {
-		bodyCopy := acquireBuffer()
-		if _, err := io.Copy(bodyCopy, bytes.NewReader(r.bodyBuf.Bytes())); err != nil {
-			// cannot use io.Copy(bodyCopy, r.bodyBuf) because io.Copy reset r.bodyBuf
-			return nil, err
-		}
-		return bodyCopy, nil
-	}
-
+func getRawRequestBodyCopy(r *Request) (*bytes.Buffer, error) {
 	// Maybe body is `io.Reader`.
 	// Note: Resty user have to watchout for large body size of `io.Reader`
 	if r.RawRequest.Body != nil {
diff --git a/middleware_test.go b/middleware_test.go
index fef6f008..84a614b8 100644
--- a/middleware_test.go
+++ b/middleware_test.go
@@ -1,6 +1,7 @@
 package resty
 
 import (
+	"bytes"
 	"net/url"
 	"testing"
 )
@@ -227,3 +228,47 @@ func Test_parseRequestURL(t *testing.T) {
 		})
 	}
 }
+
+func Test_createHTTPRequest(t *testing.T) {
+	type args struct {
+		c *Client
+		r *Request
+	}
+	tests := []struct {
+		name    string
+		args    args
+		wantErr bool
+	}{
+		{
+			name: "bodyBuf is not nil, deep copy",
+			args: args{
+				c: &Client{},
+				r: func() *Request {
+					req := &Request{}
+					req.bodyBuf = bytes.NewBufferString("test")
+					return req
+				}(),
+			},
+			wantErr: false,
+		},
+		{
+			name: "bodyBuf is nil, deep copy",
+			args: args{
+				c: &Client{},
+				r: func() *Request {
+					req := &Request{}
+					req.bodyBuf = nil
+					return req
+				}(),
+			},
+			wantErr: false,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if err := createHTTPRequest(tt.args.c, tt.args.r); (err != nil) != tt.wantErr {
+				t.Errorf("createHTTPRequest() error = %v, wantErr %v", err, tt.wantErr)
+			}
+		})
+	}
+}