diff --git a/Rakefile b/Rakefile
index a1e5316..22b97a4 100644
--- a/Rakefile
+++ b/Rakefile
@@ -13,7 +13,7 @@ require 'rake/extensiontask'
 
 task build: :compile # rubocop:disable Rake/Desc
 
-Rake::ExtensionTask.new('randomext') do |ext|
+Rake::ExtensionTask.new('ext') do |ext|
   ext.ext_dir = 'ext/numo/random'
   ext.lib_dir = 'lib/numo/random'
 end
diff --git a/ext/numo/random/randomext.cpp b/ext/numo/random/ext.cpp
similarity index 93%
rename from ext/numo/random/randomext.cpp
rename to ext/numo/random/ext.cpp
index 6fb6c96..09effb2 100644
--- a/ext/numo/random/randomext.cpp
+++ b/ext/numo/random/ext.cpp
@@ -16,9 +16,9 @@
  * limitations under the License.
  */
 
-#include "randomext.hpp"
+#include "ext.hpp"
 
-extern "C" void Init_randomext(void) {
+extern "C" void Init_ext(void) {
   rb_require("numo/narray");
 
   VALUE rb_mNumoRandom = rb_define_module_under(mNumo, "Random");
diff --git a/ext/numo/random/randomext.hpp b/ext/numo/random/ext.hpp
similarity index 99%
rename from ext/numo/random/randomext.hpp
rename to ext/numo/random/ext.hpp
index 843a20a..4eb5b73 100644
--- a/ext/numo/random/randomext.hpp
+++ b/ext/numo/random/ext.hpp
@@ -16,8 +16,8 @@
  * limitations under the License.
  */
 
-#ifndef NUMO_RANDOMEXT_HPP
-#define NUMO_RANDOMEXT_HPP 1
+#ifndef NUMO_RANDOM_EXT_HPP
+#define NUMO_RANDOM_EXT_HPP 1
 
 #include <ruby.h>
 
@@ -691,4 +691,4 @@ const rb_data_type_t RbNumoRandomPCG64::pcg64_type = {
   RUBY_TYPED_FREE_IMMEDIATELY
 };
 
-#endif /* NUMO_RANDOMEXT_HPP */
+#endif /* NUMO_RANDOM_EXT_HPP */
diff --git a/ext/numo/random/extconf.rb b/ext/numo/random/extconf.rb
index d5b8176..9f6ef96 100644
--- a/ext/numo/random/extconf.rb
+++ b/ext/numo/random/extconf.rb
@@ -26,4 +26,4 @@
 $INCFLAGS << " -I$(srcdir)/src"
 $VPATH << "$(srcdir)/src"
 
-create_makefile("numo/random/randomext")
+create_makefile("numo/random/ext")
diff --git a/lib/numo/random.rb b/lib/numo/random.rb
index 103adf3..09a86b0 100644
--- a/lib/numo/random.rb
+++ b/lib/numo/random.rb
@@ -3,5 +3,5 @@
 require 'numo/narray'
 
 require_relative 'random/version'
-require_relative 'random/randomext'
+require_relative 'random/ext'
 require_relative 'random/generator'