diff --git a/pack.c b/pack.c
index 39a5922..dd6c3f5 100644
--- a/pack.c
+++ b/pack.c
@@ -733,6 +733,12 @@ pack_pack(VALUE ary, VALUE fmt)
             bigendian_p = 1;
             goto pack_integer;
 
+	  case 'Y':		/* unsigned long 64 bit (network byte-order) */
+            signed_p = 0;
+            integer_size = 8;
+            bigendian_p = 1;
+            goto pack_integer;
+
 	  case 'v':		/* unsigned short (VAX byte-order) */
             signed_p = 0;
             integer_size = 2;
@@ -1301,6 +1307,7 @@ infected_str_new(const char *ptr, long len, VALUE str)
  *                |         |
  *      n         | Integer | 16-bit unsigned, network (big-endian) byte order
  *      N         | Integer | 32-bit unsigned, network (big-endian) byte order
+ *      Y         | Integer | 64-bit unsigned, network (big-endian) byte order
  *      v         | Integer | 16-bit unsigned, VAX (little-endian) byte order
  *      V         | Integer | 32-bit unsigned, VAX (little-endian) byte order
  *                |         |
@@ -1643,6 +1650,12 @@ pack_unpack(VALUE str, VALUE fmt)
 	    bigendian_p = 1;
 	    goto unpack_integer;
 
+	  case 'Y':		/* unsigned long 64 bit (network byte-order) */
+            signed_p = 0;
+            integer_size = 8;
+            bigendian_p = 1;
+            goto unpack_integer;
+
 	  case 'v':
 	    signed_p = 0;
 	    integer_size = 2;
diff --git a/test/ruby/test_array.rb b/test/ruby/test_array.rb
index 6724634..09fced1 100644
--- a/test/ruby/test_array.rb
+++ b/test/ruby/test_array.rb
@@ -946,6 +946,14 @@ class TestArray < Test::Unit::TestCase
     assert_equal(@cls[], a)
   end
 
+  def test_pack_64_network
+    assert_equal("\x0\x0\x0\x1\x0\x0\x0\x1", [(1 << 32) + 1].pack('Y'))
+  end
+
+  def test_unpack_64_network
+    assert_equal((1 << 32) + 1, "\x0\x0\x0\x1\x0\x0\x0\x1".unpack('Y').first)
+  end
+
   def test_pack
     a = @cls[*%w( cat wombat x yy)]
     assert_equal("catwomx  yy ", a.pack("A3A3A3A3"))