diff --git a/CHANGELOG.md b/CHANGELOG.md
index c4154223..1c29b408 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -21,5 +21,6 @@ We use *breaking :warning:* to mark changes that are not backward compatible (re
 
 ### Changed
 - [#38](https://github.com/thanos-io/objstore/pull/38) *: Upgrade minio-go version to `v7.0.45`.
+- [#39](https://github.com/thanos-io/objstore/pull/39) COS: Upgrade cos sdk version to `v0.7.40`.
 
 ### Removed
diff --git a/go.mod b/go.mod
index 4d3a1cac..0914a853 100644
--- a/go.mod
+++ b/go.mod
@@ -19,7 +19,7 @@ require (
 	github.com/pkg/errors v0.9.1
 	github.com/prometheus/client_golang v1.12.2
 	github.com/prometheus/common v0.36.0
-	github.com/tencentyun/cos-go-sdk-v5 v0.7.34
+	github.com/tencentyun/cos-go-sdk-v5 v0.7.40
 	go.uber.org/atomic v1.9.0
 	golang.org/x/oauth2 v0.0.0-20220411215720-9780585627b5
 	golang.org/x/sync v0.0.0-20220601150217-0de741cfad7f
diff --git a/go.sum b/go.sum
index 430c4129..f866cacc 100644
--- a/go.sum
+++ b/go.sum
@@ -388,8 +388,8 @@ github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/
 github.com/stretchr/testify v1.7.1 h1:5TQK59W5E3v0r2duFAb7P95B6hEeOyEnHRa8MjYSMTY=
 github.com/tencentcloud/tencentcloud-sdk-go/tencentcloud/common v1.0.194/go.mod h1:7sCQWVkxcsR38nffDW057DRGk8mUjK1Ing/EFOK8s8Y=
 github.com/tencentcloud/tencentcloud-sdk-go/tencentcloud/kms v1.0.194/go.mod h1:yrBKWhChnDqNz1xuXdSbWXG56XawEq0G5j1lg4VwBD4=
-github.com/tencentyun/cos-go-sdk-v5 v0.7.34 h1:xm+Pg+6m486y4eugRI7/E4WasbVmpY1hp9QBSRErgp8=
-github.com/tencentyun/cos-go-sdk-v5 v0.7.34/go.mod h1:4dCEtLHGh8QPxHEkgq+nFaky7yZxQuYwgSJM87icDaw=
+github.com/tencentyun/cos-go-sdk-v5 v0.7.40 h1:W6vDGKCHe4wBACI1d2UgE6+50sJFhRWU4O8IB2ozzxM=
+github.com/tencentyun/cos-go-sdk-v5 v0.7.40/go.mod h1:4dCEtLHGh8QPxHEkgq+nFaky7yZxQuYwgSJM87icDaw=
 github.com/yuin/goldmark v1.1.25/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
 github.com/yuin/goldmark v1.1.27/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
 github.com/yuin/goldmark v1.1.32/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=