diff --git a/test/ipaddress/ipv4_test.rb b/test/ipaddress/ipv4_test.rb
index 5177c75287017721a2eb250421ed6d935029aa1a..534349e78f6aabcdaa75aa876030a45d81171a83 100644
--- a/test/ipaddress/ipv4_test.rb
+++ b/test/ipaddress/ipv4_test.rb
@@ -34,7 +34,13 @@ class IPv4Test < Test::Unit::TestCase
       "172.16.0.0/16"    => 2886729728,
       "192.168.0.0/24"   => 3232235520,
       "192.168.100.4/30" => 3232261124}
-    
+
+    @hex_values = {
+      "10.0.0.0"         => "0a000000",
+      "172.16.5.4"       => "ac100504",
+      "192.168.100.4"    => "c0a86404",
+    }
+
     @ip = @klass.new("172.16.10.1/24")
     @network = @klass.new("172.16.10.0/24")
     
@@ -144,6 +150,13 @@ class IPv4Test < Test::Unit::TestCase
     end
   end
 
+  def test_method_to_hex
+    @hex_values.each do |addr,hex|
+      ip = @klass.new(addr)
+      assert_equal hex, ip.to_hex
+    end
+  end
+
   def test_method_network?
     assert_equal true, @network.network?
     assert_equal false, @ip.network?