diff --git a/lib/fluent/plugin/in_tail.rb b/lib/fluent/plugin/in_tail.rb
index a13fec4ff3..3fa13f333f 100644
--- a/lib/fluent/plugin/in_tail.rb
+++ b/lib/fluent/plugin/in_tail.rb
@@ -297,8 +297,10 @@ def extended_glob_pattern(path)
       path.include?('*') || path.include?('?') || /\[.*\]/.match(path)
     end
 
-    # Curly braces is not supported for now because the default delimiter of path is ",".
-    # This should be collided for wildcard pattern for curly braces.
+    # Curly braces is not supported with default path_delimiter
+    # because the default delimiter of path is ",".
+    # This should be collided for wildcard pattern for curly braces and
+    # be handled as a error on #configure.
     def use_glob?(path)
       if @glob_policy == :always
         # For future extensions, we decided to use `always' term to handle