diff --git a/aioupnp/util.py b/aioupnp/util.py
index 540d33e..1adfa07 100644
--- a/aioupnp/util.py
+++ b/aioupnp/util.py
@@ -1,3 +1,4 @@
+import sys
 import ipaddress
 import typing
 from collections import OrderedDict
@@ -62,7 +63,7 @@ def is_valid_public_ipv4(address):
                 parsed_ip.is_multicast, parsed_ip.is_reserved, parsed_ip.is_private, parsed_ip.is_reserved)):
             return False
         else:
-            return not any((CARRIER_GRADE_NAT_SUBNET.supernet_of(ipaddress.ip_network(f"{address}/32")),
-                            IPV4_TO_6_RELAY_SUBNET.supernet_of(ipaddress.ip_network(f"{address}/32"))))
+            return not any((CARRIER_GRADE_NAT_SUBNET.overlaps(ipaddress.ip_network(f"{address}/32")),
+                            IPV4_TO_6_RELAY_SUBNET.overlaps(ipaddress.ip_network(f"{address}/32"))))
     except (ipaddress.AddressValueError, ValueError):
         return False
diff --git a/tests/test_upnp.py b/tests/test_upnp.py
index cec00f6..4b9abf8 100644
--- a/tests/test_upnp.py
+++ b/tests/test_upnp.py
@@ -75,6 +75,18 @@ class TestGetExternalIPAddress(UPnPCommandTestCase):
                 await upnp.get_external_ip()
                 self.assertTrue(str(err).startswith("Got invalid external ipv4 address"))
 
+    async def test_handle_got_carrier_nat_ip(self):
+        request = b'POST /soap.cgi?service=WANIPConn1 HTTP/1.1\r\nHost: 11.2.3.4\r\nUser-Agent: python3/aioupnp, UPnP/1.0, MiniUPnPc/1.9\r\nContent-Length: 285\r\nContent-Type: text/xml\r\nSOAPAction: "urn:schemas-upnp-org:service:WANIPConnection:1#GetExternalIPAddress"\r\nConnection: Close\r\nCache-Control: no-cache\r\nPragma: no-cache\r\n\r\n<?xml version="1.0"?>\r\n<s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/" s:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"><s:Body><u:GetExternalIPAddress xmlns:u="urn:schemas-upnp-org:service:WANIPConnection:1"></u:GetExternalIPAddress></s:Body></s:Envelope>\r\n'
+        self.replies.update({request: b"HTTP/1.1 200 OK\r\nServer: WebServer\r\nDate: Wed, 22 May 2019 03:25:57 GMT\r\nConnection: close\r\nCONTENT-TYPE: text/xml; charset=\"utf-8\"\r\nCONTENT-LENGTH: 365 \r\nEXT:\r\n\r\n<?xml version=\"1.0\"?>\n<s:Envelope xmlns:s=\"http://schemas.xmlsoap.org/soap/envelope/\" s:encodingStyle=\"http://schemas.xmlsoap.org/soap/encoding/\">\n\t<s:Body>\n\t\t<u:GetExternalIPAddressResponse xmlns:u=\"urn:schemas-upnp-org:service:WANIPConnection:1\">\n<NewExternalIPAddress>192.88.99.2</NewExternalIPAddress>\n</u:GetExternalIPAddressResponse>\n\t</s:Body>\n</s:Envelope>\n"})
+        self.addCleanup(self.replies.pop, request)
+        with mock_tcp_and_udp(self.loop, tcp_replies=self.replies):
+            gateway = Gateway(self.reply, self.client_address, self.gateway_address, loop=self.loop)
+            await gateway.discover_commands()
+            upnp = UPnP(self.client_address, self.gateway_address, gateway)
+            with self.assertRaises(UPnPError) as err:
+                await upnp.get_external_ip()
+                self.assertTrue(str(err).startswith("Got invalid external ipv4 address"))
+
     async def test_null_external_ip(self):
         request = b'POST /soap.cgi?service=WANIPConn1 HTTP/1.1\r\nHost: 11.2.3.4\r\nUser-Agent: python3/aioupnp, UPnP/1.0, MiniUPnPc/1.9\r\nContent-Length: 285\r\nContent-Type: text/xml\r\nSOAPAction: "urn:schemas-upnp-org:service:WANIPConnection:1#GetExternalIPAddress"\r\nConnection: Close\r\nCache-Control: no-cache\r\nPragma: no-cache\r\n\r\n<?xml version="1.0"?>\r\n<s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/" s:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"><s:Body><u:GetExternalIPAddress xmlns:u="urn:schemas-upnp-org:service:WANIPConnection:1"></u:GetExternalIPAddress></s:Body></s:Envelope>\r\n'
         self.replies.update({