diff --git a/fakestorage/object.go b/fakestorage/object.go
index 62bfd86b1b..3210d9b1c2 100644
--- a/fakestorage/object.go
+++ b/fakestorage/object.go
@@ -993,9 +993,10 @@ func (s *Server) updateObject(r *http.Request) jsonResponse {
 	}
 
 	var payload struct {
-		Metadata   map[string]string `json:"metadata"`
-		CustomTime string
-		Acl        []acls
+		Metadata    map[string]string `json:"metadata"`
+		ContentType string            `json:"contentType"`
+		CustomTime  string
+		Acl         []acls
 	}
 	err := json.NewDecoder(r.Body).Decode(&payload)
 	if err != nil {
@@ -1009,7 +1010,7 @@ func (s *Server) updateObject(r *http.Request) jsonResponse {
 
 	attrsToUpdate.Metadata = payload.Metadata
 	attrsToUpdate.CustomTime = payload.CustomTime
-
+	attrsToUpdate.ContentType = payload.ContentType
 	if len(payload.Acl) > 0 {
 		attrsToUpdate.ACL = []storage.ACLRule{}
 		for _, aclData := range payload.Acl {
diff --git a/fakestorage/object_test.go b/fakestorage/object_test.go
index 48c1263175..ac3cd0ab07 100644
--- a/fakestorage/object_test.go
+++ b/fakestorage/object_test.go
@@ -1669,6 +1669,57 @@ func TestServerClientObjectUpdateCustomTime(t *testing.T) {
 	})
 }
 
+func TestServerClientObjectUpdateContentType(t *testing.T) {
+	const (
+		bucketName  = "some-bucket"
+		objectName  = "data.txt"
+		content     = "some nice content"
+		contentType = "some content-type"
+	)
+	objs := []Object{
+		{
+			ObjectAttrs: ObjectAttrs{
+				BucketName:  bucketName,
+				Name:        objectName,
+				ContentType: contentType,
+			},
+			Content: []byte(content),
+		},
+	}
+	url := fmt.Sprintf("https://storage.googleapis.com/storage/v1/b/%s/o/%s", bucketName, objectName)
+	runServersTest(t, runServersOptions{objs: objs}, func(t *testing.T, server *Server) {
+		client := server.HTTPClient()
+		jsonBody := []byte(`{"ContentType": "another content-type"}`)
+		bodyReader := bytes.NewReader(jsonBody)
+		req, err := http.NewRequest(http.MethodPost, url, bodyReader)
+		if err != nil {
+			t.Fatal(err)
+		}
+		resp, err := client.Do(req)
+		if err != nil {
+			t.Fatal(err)
+		}
+		defer resp.Body.Close()
+		if resp.StatusCode != http.StatusOK {
+			t.Errorf("wrong status returned\nwant %d\ngot  %d", http.StatusOK, resp.StatusCode)
+		}
+		data, err := io.ReadAll(resp.Body)
+		if err != nil {
+			t.Fatal(err)
+		}
+		var respJsonBody ObjectAttrs
+		err = json.Unmarshal(data, &respJsonBody)
+		if err != nil {
+			t.Fatal(err)
+		}
+		updatedContentType := respJsonBody.ContentType
+		expectedContentType := "another content-type"
+		if updatedContentType != expectedContentType {
+			t.Errorf("unexpected content type time\nwant %q\ngot  %q", expectedContentType, updatedContentType)
+		}
+	})
+}
+
 func TestServerClientObjectPatchCustomTime(t *testing.T) {
 	const (
 		bucketName  = "some-bucket"
diff --git a/fakestorage/upload.go b/fakestorage/upload.go
index 1fbb1ef849..fe1cceb641 100644
--- a/fakestorage/upload.go
+++ b/fakestorage/upload.go
@@ -485,7 +485,12 @@ func (s *Server) uploadFileContent(r *http.Request) jsonResponse {
 	obj.Crc32c = checksum.EncodedCrc32cChecksum(obj.Content)
 	obj.Md5Hash = checksum.EncodedMd5Hash(obj.Content)
 	obj.Etag = fmt.Sprintf("%q", obj.Md5Hash)
-	obj.ContentType = r.Header.Get(contentTypeHeader)
+	contentTypeHeader := r.Header.Get(contentTypeHeader)
+	if contentTypeHeader != "" {
+		obj.ContentType = contentTypeHeader
+	} else {
+		obj.ContentType = "application/octet-stream"
+	}
 	responseHeader := make(http.Header)
 	if contentRange := r.Header.Get("Content-Range"); contentRange != "" {
 		parsed, err := parseContentRange(contentRange)