diff --git a/api/handler/multipart_upload.go b/api/handler/multipart_upload.go
index e33de97..e5b9022 100644
--- a/api/handler/multipart_upload.go
+++ b/api/handler/multipart_upload.go
@@ -2,6 +2,7 @@ package handler
 
 import (
 	"encoding/xml"
+	"fmt"
 	"io"
 	"net/http"
 	"net/url"
@@ -405,11 +406,46 @@ func (h *handler) CompleteMultipartUploadHandler(w http.ResponseWriter, r *http.
 	// back to the client the same way as Amazon S3 service does.
 	stopPeriodicResponseWriter := periodicXMLWriter(w, h.cfg.CompleteMultipartKeepalive)
 
+	// Start complete multipart upload which may take some time to fetch object
+	// and re-upload it part by part.
+	objInfo, err := h.completeMultipartUpload(r, c, bktInfo, reqInfo, sessionTokenSetEACL)
+
+	// Stop periodic writer as complete multipart upload is finished
+	// successfully or not.
+	headerIsWritten := stopPeriodicResponseWriter()
+
+	responseWriter := api.EncodeToResponse
+	errLogger := h.logAndSendError
+	// Do not send XML and HTTP headers if periodic writer was invoked at this point.
+	if headerIsWritten {
+		responseWriter = api.EncodeToResponseNoHeader
+		errLogger = h.logAndSendErrorNoHeader
+	}
+
+	if err != nil {
+		errLogger(w, "complete multipart error", reqInfo, err, additional...)
+		return
+	}
+
+	response := CompleteMultipartUploadResponse{
+		Bucket: objInfo.Bucket,
+		ETag:   objInfo.HashSum,
+		Key:    objInfo.Name,
+	}
+
+	// Here we previously set api.AmzVersionID header for versioned bucket.
+	// It is not possible after #60, because of periodic white
+	// space XML writer to keep connection with the client.
+
+	if err = responseWriter(w, response); err != nil {
+		errLogger(w, "something went wrong", reqInfo, err)
+	}
+}
+
+func (h *handler) completeMultipartUpload(r *http.Request, c *layer.CompleteMultipartParams, bktInfo *data.BucketInfo, reqInfo *api.ReqInfo, stoken *session.Container) (*data.ObjectInfo, error) {
 	uploadData, extendedObjInfo, err := h.obj.CompleteMultipartUpload(r.Context(), c)
 	if err != nil {
-		logAndSendError := h.periodicWriterErrorSender(stopPeriodicResponseWriter())
-		logAndSendError(w, "could not complete multipart upload", reqInfo, err, additional...)
-		return
+		return nil, fmt.Errorf("could not complete multipart upload: %w", err)
 	}
 	objInfo := extendedObjInfo.ObjectInfo
 
@@ -424,24 +460,18 @@ func (h *handler) CompleteMultipartUploadHandler(w http.ResponseWriter, r *http.
 			NodeVersion: extendedObjInfo.NodeVersion,
 		}
 		if _, err = h.obj.PutObjectTagging(r.Context(), tagPrm); err != nil {
-			logAndSendError := h.periodicWriterErrorSender(stopPeriodicResponseWriter())
-			logAndSendError(w, "could not put tagging file of completed multipart upload", reqInfo, err, additional...)
-			return
+			return nil, fmt.Errorf("could not put tagging file of completed multipart upload: %w", err)
 		}
 	}
 
 	if len(uploadData.ACLHeaders) != 0 {
 		key, err := h.bearerTokenIssuerKey(r.Context())
 		if err != nil {
-			logAndSendError := h.periodicWriterErrorSender(stopPeriodicResponseWriter())
-			logAndSendError(w, "couldn't get gate key", reqInfo, err)
-			return
+			return nil, fmt.Errorf("couldn't get gate key: %w", err)
 		}
 		acl, err := parseACLHeaders(r.Header, key)
 		if err != nil {
-			logAndSendError := h.periodicWriterErrorSender(stopPeriodicResponseWriter())
-			logAndSendError(w, "could not parse acl", reqInfo, err)
-			return
+			return nil, fmt.Errorf("could not parse acl: %w", err)
 		}
 
 		resInfo := &resourceInfo{
@@ -450,14 +480,10 @@ func (h *handler) CompleteMultipartUploadHandler(w http.ResponseWriter, r *http.
 		}
 		astObject, err := aclToAst(acl, resInfo)
 		if err != nil {
-			logAndSendError := h.periodicWriterErrorSender(stopPeriodicResponseWriter())
-			logAndSendError(w, "could not translate acl of completed multipart upload to ast", reqInfo, err, additional...)
-			return
+			return nil, fmt.Errorf("could not translate acl of completed multipart upload to ast: %w", err)
 		}
-		if _, err = h.updateBucketACL(r, astObject, bktInfo, sessionTokenSetEACL); err != nil {
-			logAndSendError := h.periodicWriterErrorSender(stopPeriodicResponseWriter())
-			logAndSendError(w, "could not update bucket acl while completing multipart upload", reqInfo, err, additional...)
-			return
+		if _, err = h.updateBucketACL(r, astObject, bktInfo, stoken); err != nil {
+			return nil, fmt.Errorf("could not update bucket acl while completing multipart upload: %w", err)
 		}
 	}
 
@@ -471,26 +497,7 @@ func (h *handler) CompleteMultipartUploadHandler(w http.ResponseWriter, r *http.
 		h.log.Error("couldn't send notification: %w", zap.Error(err))
 	}
 
-	response := CompleteMultipartUploadResponse{
-		Bucket: objInfo.Bucket,
-		ETag:   objInfo.HashSum,
-		Key:    objInfo.Name,
-	}
-
-	// Here we previously set api.AmzVersionID header for versioned bucket.
-	// It is not possible after #60, because we introduced periodic white
-	// space XML writer to keep connection with the client.
-
-	headerIsWritten := stopPeriodicResponseWriter()
-	if headerIsWritten {
-		if err = api.EncodeToResponseNoHeader(w, response); err != nil {
-			h.logAndSendErrorNoHeader(w, "something went wrong", reqInfo, err)
-		}
-	} else {
-		if err = api.EncodeToResponse(w, response); err != nil {
-			h.logAndSendError(w, "something went wrong", reqInfo, err)
-		}
-	}
+	return objInfo, nil
 }
 
 func (h *handler) ListMultipartUploadsHandler(w http.ResponseWriter, r *http.Request) {