diff --git a/tests/sys/netpfil/pf/nat64.py b/tests/sys/netpfil/pf/nat64.py
--- a/tests/sys/netpfil/pf/nat64.py
+++ b/tests/sys/netpfil/pf/nat64.py
@@ -28,19 +28,38 @@
 import selectors
 import socket
 import sys
+import threading
+import time
 from atf_python.sys.net.tools import ToolsHelper
 from atf_python.sys.net.vnet import VnetTestTemplate
 
+class DelayedSend(threading.Thread):
+    def __init__(self, packet):
+        threading.Thread.__init__(self)
+        self._packet = packet
+
+        self.start()
+
+    def run(self):
+        import scapy.all as sp
+        time.sleep(1)
+        sp.send(self._packet)
+
 class TestNAT64(VnetTestTemplate):
     REQUIRED_MODULES = [ "pf" ]
     TOPOLOGY = {
         "vnet1": {"ifaces": ["if1"]},
         "vnet2": {"ifaces": ["if1", "if2"]},
-        "vnet3": {"ifaces": ["if2"]},
+        "vnet3": {"ifaces": ["if2", "if3"]},
+        "vnet4": {"ifaces": ["if3"]},
         "if1": {"prefixes6": [("2001:db8::2/64", "2001:db8::1/64")]},
         "if2": {"prefixes4": [("192.0.2.1/24", "192.0.2.2/24")]},
+        "if3": {"prefixes4": [("198.51.100.1/24", "198.51.100.2/24")]}
     }
 
+    def vnet4_handler(self, vnet):
+        ToolsHelper.print_output("/sbin/route add default 198.51.100.1")
+
     def vnet3_handler(self, vnet):
         ToolsHelper.print_output("/sbin/sysctl net.inet.ip.forwarding=1")
         ToolsHelper.print_output("/sbin/sysctl net.inet.ip.ttl=62")
@@ -155,7 +174,7 @@
 
         import scapy.all as sp
 
-        packet = sp.IPv6(dst="64:ff9b::198.51.100.3") \
+        packet = sp.IPv6(dst="64:ff9b::203.0.113.2") \
             / sp.UDP(dport=1222) / sp.Raw("bar")
         reply = sp.sr1(packet, timeout=3)
         print(reply.show())
@@ -193,3 +212,74 @@
         udp = reply.getlayer(sp.UDP)
         assert udp
         assert udp.chksum != 0
+
+    def common_test_source_addr(self, packet):
+        vnet = self.vnet_map["vnet1"]
+        sendif = vnet.iface_alias_map["if1"].name
+
+        import scapy.all as sp
+
+        print("Outbound:\n")
+        packet.show()
+
+        s = DelayedSend(packet)
+
+        # We expect an ICMPv6 error here, where we'll verify the source address of
+        # the outer packet
+        packets = sp.sniff(iface=sendif, timeout=5)
+
+        for reply in packets:
+            print("Reply:\n")
+            reply.show()
+            icmp = reply.getlayer(sp.ICMPv6TimeExceeded)
+            if not icmp:
+                continue
+
+            ip = reply.getlayer(sp.IPv6)
+            assert icmp
+            assert ip.src == "64:ff9b::c000:202"
+            return
+
+        # If we don't find the packet we expect to see
+        assert False
+
+    @pytest.mark.require_user("root")
+    @pytest.mark.require_progs(["scapy"])
+    def test_source_addr_tcp(self):
+        ToolsHelper.print_output("/sbin/route -6 add default 2001:db8::1")
+        import scapy.all as sp
+
+        packet = sp.IPv6(dst="64:ff9b::198.51.100.2", hlim=1) \
+            / sp.TCP(sport=1111, dport=2222, flags="S")
+        self.common_test_source_addr(packet)
+
+    @pytest.mark.require_user("root")
+    @pytest.mark.require_progs(["scapy"])
+    def test_source_addr_udp(self):
+        ToolsHelper.print_output("/sbin/route -6 add default 2001:db8::1")
+        import scapy.all as sp
+
+        packet = sp.IPv6(dst="64:ff9b::198.51.100.2", hlim=1) \
+            / sp.UDP(sport=1111, dport=2222) / sp.Raw("foo")
+        self.common_test_source_addr(packet)
+
+    @pytest.mark.require_user("root")
+    @pytest.mark.require_progs(["scapy"])
+    def test_source_addr_sctp(self):
+        ToolsHelper.print_output("/sbin/route -6 add default 2001:db8::1")
+        import scapy.all as sp
+
+        packet = sp.IPv6(dst="64:ff9b::198.51.100.2", hlim=1) \
+            / sp.SCTP(sport=1111, dport=2222) \
+            / sp.SCTPChunkInit(init_tag=1, n_in_streams=1, n_out_streams=1, a_rwnd=1500)
+        self.common_test_source_addr(packet)
+
+    @pytest.mark.require_user("root")
+    @pytest.mark.require_progs(["scapy"])
+    def test_source_addr_icmp(self):
+        ToolsHelper.print_output("/sbin/route -6 add default 2001:db8::1")
+        import scapy.all as sp
+
+        packet = sp.IPv6(dst="64:ff9b::198.51.100.2", hlim=1) \
+            / sp.ICMPv6EchoRequest() / sp.Raw("foo")
+        self.common_test_source_addr(packet)