diff --git a/apps/emqx_s3/src/emqx_s3.app.src b/apps/emqx_s3/src/emqx_s3.app.src
index c307f2c9c..f9374bfd9 100644
--- a/apps/emqx_s3/src/emqx_s3.app.src
+++ b/apps/emqx_s3/src/emqx_s3.app.src
@@ -1,6 +1,6 @@
 {application, emqx_s3, [
     {description, "EMQX S3"},
-    {vsn, "5.1.0"},
+    {vsn, "5.1.1"},
     {modules, []},
     {registered, [emqx_s3_sup]},
     {applications, [
diff --git a/apps/emqx_s3/src/emqx_s3_schema.erl b/apps/emqx_s3/src/emqx_s3_schema.erl
index efef32aa0..a8d6c8750 100644
--- a/apps/emqx_s3/src/emqx_s3_schema.erl
+++ b/apps/emqx_s3/src/emqx_s3_schema.erl
@@ -121,7 +121,7 @@ fields(s3_uploader) ->
                 #{
                     default => <<"5mb">>,
                     desc => ?DESC("min_part_size"),
-                    required => true,
+                    required => false,
                     validator => fun part_size_validator/1
                 }
             )},
@@ -131,7 +131,7 @@ fields(s3_uploader) ->
                 #{
                     default => <<"5gb">>,
                     desc => ?DESC("max_part_size"),
-                    required => true,
+                    required => false,
                     validator => fun part_size_validator/1
                 }
             )}