diff --git a/lib/ipaddr.rb b/lib/ipaddr.rb
index eb018a5..54c21c8 100644
--- a/lib/ipaddr.rb
+++ b/lib/ipaddr.rb
@@ -374,6 +374,11 @@ def succ
     return self.clone.set(@addr + 1, @family)
   end
 
+  # Returns a new ipaddr without a mask
+  def unmasked
+    self.class.new(@unmasked_addr, @family)
+  end
+
   # Compares the ipaddr with another.
   def <=>(other)
     other = coerce_other(other)
@@ -504,6 +509,7 @@ def set(addr, *family)
       raise AddressFamilyError, "unsupported address family"
     end
     @addr = addr
+    @unmasked_addr = addr
     if family[0]
       @family = family[0]
     end
@@ -616,6 +622,7 @@ def initialize(addr = '::', family = Socket::AF_UNSPEC)
     if family != Socket::AF_UNSPEC && @family != family
       raise AddressFamilyError, "address family mismatch"
     end
+    @unmasked_addr = @addr
     if prefixlen
       mask!(prefixlen)
     else
diff --git a/test/test_ipaddr.rb b/test/test_ipaddr.rb
index edfdbd2..52ccaef 100644
--- a/test/test_ipaddr.rb
+++ b/test/test_ipaddr.rb
@@ -422,4 +422,13 @@ def test_hash
     assert_equal(true, s.include?(a5))
     assert_equal(true, s.include?(a6))
   end
+
+  def test_unmasked
+    assert_equal(IPAddr.new("1.2.3.4"), IPAddr.new("1.2.3.4").unmasked)
+    assert_equal(IPAddr.new("1.2.3.4"), IPAddr.new("1.2.3.4/8").unmasked)
+    assert_equal(IPAddr.new("0001:0002:0000:0000:0000:0000:0000:0003"), IPAddr.new("1:2::3").unmasked)
+    assert_equal(IPAddr.new("0001:0002:0000:0000:0000:0000:0000:0003"), IPAddr.new("1:2::3/16").unmasked)
+    assert_equal(IPAddr.new("1.2.3.4"), IPAddr.new(IPAddr.new("1.2.3.4").to_i, Socket::AF_INET).unmasked)
+    assert_equal(IPAddr.new("1.2.3.5"), IPAddr.new("1.2.3.4").succ.mask(8).unmasked)
+  end
 end