diff --git a/lib/fluent/capability.rb b/lib/fluent/capability.rb
index fad490a1ae..9c2acf30d9 100644
--- a/lib/fluent/capability.rb
+++ b/lib/fluent/capability.rb
@@ -26,7 +26,7 @@
 module Fluent
   if defined?(CapNG)
     class Capability
-      def initialize(target = :current_process, pid_or_path = nil)
+      def initialize(target = :current_process, pid = nil)
         @capng = CapNG.new(target, pid_or_path)
       end
 
@@ -56,7 +56,7 @@ def have_capabilities?(select_set)
     end
   else
     class Capability
-      def initialize(target = :current_process, pid_or_path = nil)
+      def initialize(target = :current_process, pid = nil)
       end
 
       def usable?