diff --git a/ext/io/console/console.c b/ext/io/console/console.c
index 6fd8677a3c..0448a6cba8 100644
--- a/ext/io/console/console.c
+++ b/ext/io/console/console.c
@@ -2,6 +2,10 @@
 /*
  * console IO module
  */
+
+static const char *const
+IO_CONSOLE_VERSION = "0.7.2.dev.1";
+
 #include "ruby.h"
 #include "ruby/io.h"
 #include "ruby/thread.h"
diff --git a/ext/io/console/extconf.rb b/ext/io/console/extconf.rb
index aa0b6c6cfb..a72403c7f9 100644
--- a/ext/io/console/extconf.rb
+++ b/ext/io/console/extconf.rb
@@ -1,11 +1,6 @@
 # frozen_string_literal: false
 require 'mkmf'
 
-version = ["../../..", "."].find do |dir|
-  break File.read(File.join(__dir__, dir, "io-console.gemspec"))[/^_VERSION\s*=\s*"(.*?)"/, 1]
-rescue
-end
-
 have_func("rb_io_path")
 have_func("rb_io_descriptor")
 have_func("rb_io_get_write_io")
@@ -40,7 +35,6 @@ when true
   elsif have_func("rb_scheduler_timeout") # 3.0
     have_func("rb_io_wait")
   end
-  $defs << "-D""IO_CONSOLE_VERSION=#{version}"
   create_makefile("io/console") {|conf|
     conf << "\n""VK_HEADER = #{vk_header}\n"
   }
diff --git a/ext/io/console/io-console.gemspec b/ext/io/console/io-console.gemspec
index c5e713fef1..f9c1729cb7 100644
--- a/ext/io/console/io-console.gemspec
+++ b/ext/io/console/io-console.gemspec
@@ -1,5 +1,13 @@
 # -*- ruby -*-
-_VERSION = "0.7.2.dev.1"
+_VERSION = ["", "ext/io/console/"].find do |dir|
+  begin
+    break File.open(File.join(__dir__, "#{dir}console.c")) {|f|
+      f.gets("\nIO_CONSOLE_VERSION ")
+      f.gets[/"(.+)"/, 1]
+    }
+  rescue Errno::ENOENT
+  end
+end
 
 Gem::Specification.new do |s|
   s.name = "io-console"