diff --git a/lib/reline.rb b/lib/reline.rb
index 4c26ac7266..52a4b3c78f 100644
--- a/lib/reline.rb
+++ b/lib/reline.rb
@@ -36,7 +36,6 @@ module Reline
     attr_accessor :config
     attr_accessor :key_stroke
     attr_accessor :line_editor
-    attr_writer :ambiguous_width
     attr_accessor :last_incremental_search
     attr_reader :output