diff --git a/Rakefile b/Rakefile
index 7e307dcb..0945a67c 100644
--- a/Rakefile
+++ b/Rakefile
@@ -331,6 +331,8 @@ else
       end
       src = File.read("parser.c").gsub(/[ \t]+$/, '')
       src.gsub!(/^static const int (JSON_.*=.*);$/, 'enum {\1};')
+      src.gsub!(/0 <= \(\*p\) && \(\*p\) <= 31/, "0 <= (signed char)(*p) && (*p) <= 31")
+      src[0, 0] = "/* This file is automatically generated from parser.rl by using ragel */"
       File.open("parser.c", "w") {|f| f.print src}
     end
   end
diff --git a/ext/json/ext/parser/parser.c b/ext/json/ext/parser/parser.c
index bc4ac46e..e4a30566 100644
--- a/ext/json/ext/parser/parser.c
+++ b/ext/json/ext/parser/parser.c
@@ -1,4 +1,4 @@
-
+/* This file is automatically generated from parser.rl by using ragel */
 #line 1 "parser.rl"
 #include "../fbuffer/fbuffer.h"
 #include "parser.h"
@@ -1563,7 +1563,7 @@ case 2:
 		case 34: goto tr2;
 		case 92: goto st3;
 	}
-	if ( 0 <= (*p) && (*p) <= 31 )
+	if ( 0 <= (signed char)(*p) && (*p) <= 31 )
 		goto st0;
 	goto st2;
 tr2:
@@ -1593,7 +1593,7 @@ case 8:
 case 3:
 	if ( (*p) == 117 )
 		goto st4;
-	if ( 0 <= (*p) && (*p) <= 31 )
+	if ( 0 <= (signed char)(*p) && (*p) <= 31 )
 		goto st0;
 	goto st2;
 st4:
diff --git a/json.gemspec b/json.gemspec
index a101aba9..0c72e824 100644
--- a/json.gemspec
+++ b/json.gemspec
@@ -131,7 +131,6 @@ Gem::Specification.new do |s|
   s.licenses = ["Ruby"]
   s.rdoc_options = ["--title", "JSON implemention for Ruby", "--main", "README.md"]
   s.required_ruby_version = Gem::Requirement.new(">= 2.0")
-  s.rubygems_version = "3.0.2"
   s.summary = "JSON Implementation for Ruby"
   s.test_files = ["tests/test_helper.rb"]