diff --git a/backend.go b/backend.go
index f5334b1..aba93b7 100644
--- a/backend.go
+++ b/backend.go
@@ -318,7 +318,7 @@ type MultipartBackend interface {
 	ListParts(bucket, object string, uploadID UploadID, marker int, limit int64) (*ListMultipartUploadPartsResult, error)
 
 	AbortMultipartUpload(bucket, object string, id UploadID) error
-	CompleteMultipartUpload(bucket, object string, id UploadID, input *CompleteMultipartUploadRequest) (*CompleteMultipartResult, error)
+	CompleteMultipartUpload(bucket, object string, id UploadID, input *CompleteMultipartUploadRequest) (*CompleteMultipartUploadResult, error)
 }
 
 // CopyObject is a helper function useful for quickly implementing CopyObject on
diff --git a/gofakes3.go b/gofakes3.go
index 8fe0456..66c0284 100644
--- a/gofakes3.go
+++ b/gofakes3.go
@@ -788,9 +788,12 @@ func (g *GoFakeS3) copyObject(bucket, object string, meta map[string]string, w h
 	if srcObj.VersionID != "" {
 		w.Header().Set("x-amz-version-id", string(srcObj.VersionID))
 	}
-	if result.ETag != "" {
-		w.Header().Set("ETag", result.ETag)
+
+	etag := result.ETag
+	if etag == "" {
+		etag = formatETag(hex.EncodeToString(srcObj.Hash))
 	}
+	w.Header().Set("ETag", etag)
 
 	return g.xmlEncoder(w).Encode(result)
 }
@@ -987,7 +990,7 @@ func (g *GoFakeS3) completeMultipartUpload(bucket, object string, uploadID Uploa
 		w.Header().Set("x-amz-version-id", string(res.VersionID))
 	}
 
-	return g.xmlEncoder(w).Encode(&CompleteMultipartUploadResult{
+	return g.xmlEncoder(w).Encode(&CompleteMultipartUploadResponse{
 		ETag:   res.ETag,
 		Bucket: bucket,
 		Key:    object,
diff --git a/messages.go b/messages.go
index 6d51a2f..1075421 100644
--- a/messages.go
+++ b/messages.go
@@ -69,7 +69,7 @@ func (c CompleteMultipartUploadRequest) partIDs() []int {
 	return inParts
 }
 
-type CompleteMultipartUploadResult struct {
+type CompleteMultipartUploadResponse struct {
 	Location string `xml:"Location"`
 	Bucket   string `xml:"Bucket"`
 	Key      string `xml:"Key"`
@@ -369,7 +369,7 @@ type UploadPartResult struct {
 	ETag string `xml:"ETag,omitempty"`
 }
 
-type CompleteMultipartResult struct {
+type CompleteMultipartUploadResult struct {
 	// If versioning is enabled on the bucket, this should be set to the
 	// created version ID. If versioning is not enabled, this should be
 	// empty.
diff --git a/uploader.go b/uploader.go
index c77cb85..ad47be3 100644
--- a/uploader.go
+++ b/uploader.go
@@ -403,7 +403,7 @@ func (u *uploader) UploadPart(bucket, object string, id UploadID, partNumber int
 	return &UploadPartResult{ETag: formatETag(etag)}, nil
 }
 
-func (u *uploader) CompleteMultipartUpload(bucket, object string, id UploadID, input *CompleteMultipartUploadRequest) (*CompleteMultipartResult, error) {
+func (u *uploader) CompleteMultipartUpload(bucket, object string, id UploadID, input *CompleteMultipartUploadRequest) (*CompleteMultipartUploadResult, error) {
 	mpu, err := u.getUnlocked(bucket, object, id)
 	if err != nil {
 		return nil, err
@@ -457,7 +457,7 @@ func (u *uploader) CompleteMultipartUpload(bucket, object string, id UploadID, i
 
 	// if getUnlocked succeeded, so will this:
 	u.buckets[bucket].remove(id)
-	return &CompleteMultipartResult{
+	return &CompleteMultipartUploadResult{
 		VersionID: result.VersionID,
 		ETag:      etag,
 	}, nil