diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 381a35e..23714e8 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -7,7 +7,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        ruby: [ 'head', '3.0', '2.7', '2.6', '2.5' ]
+        ruby: [ 'head', '3.0', '2.7', '2.6', '2.5', '2.4', '2.3' ]
         os: [ 'ubuntu-latest', 'windows-latest' ]
         include:
           - { os: macos-latest, ruby: '2.6' }
diff --git a/fileutils.gemspec b/fileutils.gemspec
index 76baea3..53c32e7 100644
--- a/fileutils.gemspec
+++ b/fileutils.gemspec
@@ -18,7 +18,7 @@ Gem::Specification.new do |s|
 
   s.require_path = %w{lib}
   s.files = ["LICENSE.txt", "README.md", "Rakefile", "fileutils.gemspec", "lib/fileutils.rb"]
-  s.required_ruby_version = ">= 2.5.0"
+  s.required_ruby_version = ">= 2.3.0"
 
   s.authors = ["Minero Aoki"]
   s.email = [nil]
diff --git a/lib/fileutils.rb b/lib/fileutils.rb
index 69de458..a2ad0c0 100644
--- a/lib/fileutils.rb
+++ b/lib/fileutils.rb
@@ -837,8 +837,13 @@ def compare_file(a, b)
   def compare_stream(a, b)
     bsize = fu_stream_blksize(a, b)
 
-    sa = String.new(capacity: bsize)
-    sb = String.new(capacity: bsize)
+    if RUBY_VERSION > "2.4"
+      sa = String.new(capacity: bsize)
+      sb = String.new(capacity: bsize)
+    else
+      sa = String.new
+      sb = String.new
+    end
 
     begin
       a.read(bsize, sa)
@@ -1287,7 +1292,12 @@ def entries
       opts = {}
       opts[:encoding] = fu_windows? ? ::Encoding::UTF_8 : path.encoding
 
-      files = Dir.children(path, **opts)
+      files = if Dir.respond_to?(:children)
+        Dir.children(path, **opts)
+      else
+        Dir.entries(path(), **opts)
+           .reject {|n| n == '.' or n == '..' }
+      end
 
       untaint = RUBY_VERSION < '2.7'
       files.map {|n| Entry_.new(prefix(), join(rel(), untaint ? n.untaint : n)) }