diff --git a/README.rdoc b/README.rdoc
index bcb66f7..2146384 100644
--- a/README.rdoc
+++ b/README.rdoc
@@ -489,7 +489,7 @@ instance the following two networks:
 These two networks can be expressed using only one IP address
 network if we change the prefix. Let Ruby do the work:
 
-  IPAddress::IPv4::summarize(ip1,ip2).to_string
+  IPAddress::IPv4::summarize(ip1,ip2).map(&:to_string)
     #=> "172.16.10.0/23"
 
 We note how the network "172.16.10.0/23" includes all the
diff --git a/lib/ipaddress.rb b/lib/ipaddress.rb
index 0b7bd00..7631952 100644
--- a/lib/ipaddress.rb
+++ b/lib/ipaddress.rb
@@ -135,15 +135,10 @@ def self.valid_ipv4_netmask?(addr)
   #   IPAddress::valid_ipv6? "2002::DEAD::BEEF"
   #     #=> false
   #
-  def self.valid_ipv6?(addr)
-    # IPv6 (normal)
-    return true if /\A[\dA-Fa-f]{1,4}(:[\dA-Fa-f]{1,4})*\Z/ =~ addr
-    return true if /\A[\dA-Fa-f]{1,4}(:[\dA-Fa-f]{1,4})*::([\dA-Fa-f]{1,4}(:[\dA-Fa-f]{1,4})*)?\Z/ =~ addr
-    return true if /\A::([\dA-Fa-f]{1,4}(:[\dA-Fa-f]{1,4})*)?\Z/ =~ addr
-    # IPv6 (IPv4 compat)
-    return true if /\A[\dA-Fa-f]{1,4}(:[\dA-Fa-f]{1,4})*:/ =~ addr && valid_ipv4?($')
-    return true if /\A[\dA-Fa-f]{1,4}(:[\dA-Fa-f]{1,4})*::([\dA-Fa-f]{1,4}(:[\dA-Fa-f]{1,4})*:)?/ =~ addr && valid_ipv4?($')
-    return true if /\A::([\dA-Fa-f]{1,4}(:[\dA-Fa-f]{1,4})*:)?/ =~ addr && valid_ipv4?($')
+  def self.valid_ipv6?(addr) 
+    # https://gist.github.com/cpetschnig/294476
+    # http://forums.intermapper.com/viewtopic.php?t=452
+    return true if /^\s*((([0-9A-Fa-f]{1,4}:){7}([0-9A-Fa-f]{1,4}|:))|(([0-9A-Fa-f]{1,4}:){6}(:[0-9A-Fa-f]{1,4}|((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3})|:))|(([0-9A-Fa-f]{1,4}:){5}(((:[0-9A-Fa-f]{1,4}){1,2})|:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3})|:))|(([0-9A-Fa-f]{1,4}:){4}(((:[0-9A-Fa-f]{1,4}){1,3})|((:[0-9A-Fa-f]{1,4})?:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3}))|:))|(([0-9A-Fa-f]{1,4}:){3}(((:[0-9A-Fa-f]{1,4}){1,4})|((:[0-9A-Fa-f]{1,4}){0,2}:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3}))|:))|(([0-9A-Fa-f]{1,4}:){2}(((:[0-9A-Fa-f]{1,4}){1,5})|((:[0-9A-Fa-f]{1,4}){0,3}:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3}))|:))|(([0-9A-Fa-f]{1,4}:){1}(((:[0-9A-Fa-f]{1,4}){1,6})|((:[0-9A-Fa-f]{1,4}){0,4}:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3}))|:))|(:(((:[0-9A-Fa-f]{1,4}){1,7})|((:[0-9A-Fa-f]{1,4}){0,5}:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3}))|:)))(%.+)?\s*$/ =~ addr
     false
   end
 
diff --git a/test/ipaddress/ipv6_test.rb b/test/ipaddress/ipv6_test.rb
index 110e840..039356d 100644
--- a/test/ipaddress/ipv6_test.rb
+++ b/test/ipaddress/ipv6_test.rb
@@ -31,7 +31,8 @@ def setup
       "1080::8:800:200C:417A" => 21932261930451111902915077091070067066}
       
     @invalid_ipv6 = [":1:2:3:4:5:6:7",
-                     ":1:2:3:4:5:6:7"]
+                     ":1:2:3:4:5:6:7",
+                     "2002:516:2:200"]
 
     @networks = {
       "2001:db8:1:1:1:1:1:1/32" => "2001:db8::/32",
@@ -261,7 +262,7 @@ def test_classmethod_expand
     compressed = "2001:db8:0:cd30::"
     expanded = "2001:0db8:0000:cd30:0000:0000:0000:0000"
     assert_equal expanded, @klass.expand(compressed)
-    assert_not_equal expanded, @klass.expand("2001:0db8:0:cd3")
+    assert_not_equal expanded, @klass.expand("2001:0db8:0::cd3")
     assert_not_equal expanded, @klass.expand("2001:0db8::cd30")
     assert_not_equal expanded, @klass.expand("2001:0db8::cd3")
   end
@@ -270,7 +271,7 @@ def test_classmethod_compress
     compressed = "2001:db8:0:cd30::"
     expanded = "2001:0db8:0000:cd30:0000:0000:0000:0000"
     assert_equal compressed, @klass.compress(expanded)
-    assert_not_equal compressed, @klass.compress("2001:0db8:0:cd3")
+    assert_not_equal compressed, @klass.compress("2001:0db8:0::cd3")
     assert_not_equal compressed, @klass.compress("2001:0db8::cd30")
     assert_not_equal compressed, @klass.compress("2001:0db8::cd3")
   end
diff --git a/test/ipaddress_test.rb b/test/ipaddress_test.rb
index ed72aed..8e2bb66 100644
--- a/test/ipaddress_test.rb
+++ b/test/ipaddress_test.rb
@@ -43,6 +43,8 @@ def test_module_method_valid?
     assert_equal false, IPAddress::valid?("10.0.0")
     assert_equal false, IPAddress::valid?("10.0")
     assert_equal false, IPAddress::valid?("2002:::1")
+    assert_equal false, IPAddress::valid?("2002:516:2:200")
+
   end
 
   def test_module_method_valid_ipv4_netmark?