diff --git a/.github/workflows/test.yaml b/.github/workflows/test.yaml
index 1c2fe482..1ca4a6e9 100644
--- a/.github/workflows/test.yaml
+++ b/.github/workflows/test.yaml
@@ -57,7 +57,7 @@ jobs:
 
       - name: Check for parser.rb is up to date
         run: |
-          bundle exec rake build:racc_parser
+          bundle exec rake build:parser
           git diff --color --no-ext-diff --ignore-submodules --exit-code lib/lrama/parser.rb
   steep-check:
     runs-on: ubuntu-20.04
diff --git a/Rakefile b/Rakefile
index bc713a27..d1d5a570 100644
--- a/Rakefile
+++ b/Rakefile
@@ -1,13 +1,8 @@
 require "bundler/gem_tasks"
 
 namespace "build" do
-  desc "build parser from parser.y by using Racc"
-  task :racc_parser do
-    sh "bundle exec racc parser.y --embedded -o lib/lrama/parser.rb"
-  end
-
-  desc "build parser for debugging"
-  task :racc_verbose_parser do
+  desc "build parser from parser.y"
+  task :parser do
     sh "bundle exec racc parser.y --embedded -o lib/lrama/parser.rb -t --log-file=parser.output"
   end
 end
diff --git a/lib/lrama/command.rb b/lib/lrama/command.rb
index afaecda5..ee3c1d31 100644
--- a/lib/lrama/command.rb
+++ b/lib/lrama/command.rb
@@ -8,7 +8,7 @@ def run(argv)
       warning = Lrama::Warning.new
       text = options.y.read
       options.y.close if options.y != STDIN
-      grammar = Lrama::Parser.new(text, options.grammar_file).parse
+      grammar = Lrama::Parser.new(text, options.grammar_file, options.debug).parse
       states = Lrama::States.new(grammar, warning, trace_state: (options.trace_opts[:automaton] || options.trace_opts[:closure]))
       states.compute
       context = Lrama::Context.new(states)
diff --git a/lib/lrama/option_parser.rb b/lib/lrama/option_parser.rb
index b0415cdf..e52d03bf 100644
--- a/lib/lrama/option_parser.rb
+++ b/lib/lrama/option_parser.rb
@@ -58,6 +58,7 @@ def parse_by_option_parser(argv)
         o.separator 'Tuning the Parser:'
         o.on('-S', '--skeleton=FILE', 'specify the skeleton to use') {|v| @options.skeleton = v }
         o.on('-t', 'reserved, do nothing') { }
+        o.on('--debug', 'display debugging outputs of internal parser') {|v| @options.debug = true }
         o.separator ''
         o.separator 'Output:'
         o.on('-H', '--header=[FILE]', 'also produce a header file named FILE') {|v| @options.header = true; @options.header_file = v }
diff --git a/lib/lrama/options.rb b/lib/lrama/options.rb
index 01b3e701..007661f6 100644
--- a/lib/lrama/options.rb
+++ b/lib/lrama/options.rb
@@ -4,7 +4,8 @@ class Options
     attr_accessor :skeleton, :header, :header_file,
                   :report_file, :outfile,
                   :error_recovery, :grammar_file,
-                  :report_file, :trace_opts, :report_opts, :y
+                  :report_file, :trace_opts, :report_opts, :y,
+                  :debug
 
     def initialize
       @skeleton = "bison/yacc.c"
diff --git a/lib/lrama/parser.rb b/lib/lrama/parser.rb
index 96d0bd46..2448726d 100644
--- a/lib/lrama/parser.rb
+++ b/lib/lrama/parser.rb
@@ -672,9 +672,10 @@ class Parser < Racc::Parser
 
 include Lrama::Report::Duration
 
-def initialize(text, path)
+def initialize(text, path, debug = false)
   @text = text
   @path = path
+  @yydebug = debug
 end
 
 def parse
@@ -1102,7 +1103,7 @@ def on_error(error_token_id, error_value, value_stack)
   "generic_symlist_item" ]
 Ractor.make_shareable(Racc_token_to_s_table) if defined?(Ractor)
 
-Racc_debug_parser = false
+Racc_debug_parser = true
 
 ##### State transition tables end #####
 
diff --git a/parser.y b/parser.y
index 47253c65..18c59f8f 100644
--- a/parser.y
+++ b/parser.y
@@ -388,9 +388,10 @@ end
 
 include Lrama::Report::Duration
 
-def initialize(text, path)
+def initialize(text, path, debug = false)
   @text = text
   @path = path
+  @yydebug = debug
 end
 
 def parse
diff --git a/spec/lrama/option_parser_spec.rb b/spec/lrama/option_parser_spec.rb
index 023720d3..2bf12ca2 100644
--- a/spec/lrama/option_parser_spec.rb
+++ b/spec/lrama/option_parser_spec.rb
@@ -47,6 +47,7 @@
           Tuning the Parser:
               -S, --skeleton=FILE              specify the skeleton to use
               -t                               reserved, do nothing
+                  --debug                      display debugging outputs of internal parser
 
           Output:
               -H, --header=[FILE]              also produce a header file named FILE