diff --git a/lib/fog/aliyun/requests/storage/get_object_http_url.rb b/lib/fog/aliyun/requests/storage/get_object_http_url.rb
index 12a9b70..9b12e3d 100644
--- a/lib/fog/aliyun/requests/storage/get_object_http_url.rb
+++ b/lib/fog/aliyun/requests/storage/get_object_http_url.rb
@@ -22,7 +22,7 @@ def get_object_http_url_public(object, expires, options = {})
           location = get_bucket_location(bucket)
 
           if acl == 'private'
-            expires_time = (Time.now.to_i + expires).to_s
+            expires_time = (Time.now.to_i + (expires.nil? ? 0 : expires.to_i)).to_s
             resource = bucket + '/' + object
             signature = sign('GET', expires_time, nil, resource)
             'http://' + bucket + '.' + location + '.aliyuncs.com/' + object +
diff --git a/lib/fog/aliyun/requests/storage/get_object_https_url.rb b/lib/fog/aliyun/requests/storage/get_object_https_url.rb
index e1a4ae8..d7a2fb8 100644
--- a/lib/fog/aliyun/requests/storage/get_object_https_url.rb
+++ b/lib/fog/aliyun/requests/storage/get_object_https_url.rb
@@ -22,7 +22,7 @@ def get_object_https_url_public(object, expires, options = {})
           location = get_bucket_location(bucket)
 
           if acl == 'private'
-            expires_time = (Time.now.to_i + expires).to_s
+            expires_time = (Time.now.to_i + (expires.nil? ? 0 : expires.to_i)).to_s
             resource = bucket + '/' + object
             signature = sign('GET', expires_time, nil, resource)
             'https://' + bucket + '.' + location + '.aliyuncs.com/' + object +