diff --git a/lib/fluent/supervisor.rb b/lib/fluent/supervisor.rb
index d97e8614f6..f27ff1e318 100644
--- a/lib/fluent/supervisor.rb
+++ b/lib/fluent/supervisor.rb
@@ -240,6 +240,7 @@ def self.load_config(path, params = {})
           logger_initializer: logger_initializer,
           chuser: chuser,
           chgroup: chgroup,
+          chumask: 0,
           suppress_repeated_stacktrace: suppress_repeated_stacktrace,
           daemonize: daemonize,
           rpc_endpoint: rpc_endpoint,