diff --git a/tests/test_cli.py b/tests/test_cli.py
index 90b5ba35f..ad0f9e409 100644
--- a/tests/test_cli.py
+++ b/tests/test_cli.py
@@ -1105,11 +1105,12 @@ c.add_valid("--network bridge:mybr0,model=e1000")  # --network bridge:
 c.add_valid("--network network:default --mac RANDOM")  # VirtualNetwork with a random macaddr
 c.add_valid("--vnc --keymap=local")  # --keymap local
 c.add_valid("--panic 0x505")  # ISA panic with iobase specified
+c.add_valid("--mac 22:11:11:11:11:11 --check mac_in_use=off")  # colliding mac, but check is skipped
+c.add_invalid("--mac 22:11:11:11:11:11")  # Colliding macaddr will error
 c.add_invalid("--graphics vnc --vnclisten 1.2.3.4")  # mixing old and new
 c.add_invalid("--network=FOO")  # Nonexistent network
 c.add_invalid("--mac 1234")  # Invalid mac
 c.add_invalid("--network user --bridge foo0")  # Mixing bridge and network
-c.add_invalid("--connect %(URI-TEST-FULL)s --mac 22:22:33:12:34:AB")  # Colliding macaddr
 
 c = vinst.add_category("storage-back-compat", "--pxe --noautoconsole")
 c.add_valid("--file %(EXISTIMG1)s --nonsparse --file-size 4")  # Existing file, other opts
@@ -1321,6 +1322,8 @@ c.add_valid("--original-xml " + _CLONE_UNMANAGED + " --auto-clone")  # Auto flag
 c.add_valid("--connect %(URI-TEST-FULL)s -o test-clone --auto-clone --clone-running --nonsparse")  # Auto flag, actual VM, skip state check
 c.add_valid("--connect %(URI-TEST-FULL)s -o test-clone-simple -n newvm --preserve-data --file %(EXISTIMG1)s")  # Preserve data shouldn't complain about existing volume
 c.add_valid("-n clonetest --original-xml " + _CLONE_UNMANAGED + " --file %(EXISTIMG3)s --file %(EXISTIMG4)s --check path_exists=off")  # Skip existing file check
+c.add_valid("-n clonetest --original-xml " + _CLONE_UNMANAGED + " --auto-clone --mac 22:11:11:11:11:11 --check all=off")  # Colliding mac but we skip the check
+c.add_invalid("-n clonetest --original-xml " + _CLONE_UNMANAGED + " --auto-clone --mac 22:11:11:11:11:11", grep="--check mac_in_use=off")  # Colliding mac should fail
 c.add_invalid("--auto-clone")  # Just the auto flag
 c.add_invalid("-o test --clone-running --file foo")  # Didn't specify new name
 c.add_invalid("-o test --clone-running --auto-clone -n test")  # new name raises error
diff --git a/tests/test_xmlconfig.py b/tests/test_xmlconfig.py
index 3596739b5..73d91bfbc 100644
--- a/tests/test_xmlconfig.py
+++ b/tests/test_xmlconfig.py
@@ -268,6 +268,9 @@ class TestXMLMisc(unittest.TestCase):
         self.assertTrue(qemumac != testmac)
         self.assertTrue(len(randommac) == len(testmac))
 
+        # Ensure is_conflict_net doesn't error on None
+        virtinst.DeviceInterface.is_conflict_net(self.conn, None)
+
     def test_support_misc(self):
         try:
             self.conn.lookupByName("foobar-idontexist")
diff --git a/virtManager/device/netlist.py b/virtManager/device/netlist.py
index 0e70b6d47..4e4c08e67 100644
--- a/virtManager/device/netlist.py
+++ b/virtManager/device/netlist.py
@@ -298,6 +298,7 @@ class vmmNetworkList(vmmGObjectUI):
 
     def validate_device(self, net):
         self._check_network_is_running(net)
+        virtinst.DeviceInterface.is_conflict_net(net.conn, net.macaddr)
         net.validate()
 
     def reset_state(self):
diff --git a/virtinst/cli.py b/virtinst/cli.py
index c6a39121e..a43d87172 100644
--- a/virtinst/cli.py
+++ b/virtinst/cli.py
@@ -311,18 +311,35 @@ def check_path_search(conn, path):
         path, searchdata.user, searchdata.fixlist)  # pragma: no cover
 
 
+def _optional_fail(msg, checkname, warn_on_skip=True):
+    """
+    Handle printing a message with an associated --check option
+    """
+    do_check = get_global_state().get_validation_check(checkname)
+    if do_check:
+        fail(msg + (_(" (Use --check %s=off or "
+            "--check all=off to override)") % checkname))
+
+    log.debug("Skipping --check %s error condition '%s'",
+        checkname, msg)
+    if warn_on_skip:
+        log.warning(msg)
+
+
+def validate_mac(conn, macaddr):
+    """
+    There's legitimate use cases for creating/cloning VMs with duplicate
+    MACs, so we do the collision check here but allow it to be skipped
+    with --check
+    """
+    try:
+        DeviceInterface.is_conflict_net(conn, macaddr)
+        return
+    except Exception as e:
+        _optional_fail(str(e), "mac_in_use")
+
+
 def validate_disk(dev, warn_overwrite=False):
-    def _optional_fail(msg, checkname, warn_on_skip=True):
-        do_check = get_global_state().get_validation_check(checkname)
-        if do_check:
-            fail(msg + (_(" (Use --check %s=off or "
-                "--check all=off to override)") % checkname))
-
-        log.debug("Skipping --check %s error condition '%s'",
-            checkname, msg)
-        if warn_on_skip:
-            log.warning(msg)
-
     def check_path_exists(dev):
         """
         Prompt if disk file already exists and preserve mode is not used
@@ -1586,6 +1603,8 @@ class ParserCheck(VirtCLIParser):
                     cb=cls.set_cb, lookup_cb=None)
         cls.add_arg("path_exists", None, is_onoff=True,
                     cb=cls.set_cb, lookup_cb=None)
+        cls.add_arg("mac_in_use", None, is_onoff=True,
+                    cb=cls.set_cb, lookup_cb=None)
         cls.add_arg("all", "all_checks", is_onoff=True)
 
     def set_cb(self, inst, val, virtarg):
diff --git a/virtinst/cloner.py b/virtinst/cloner.py
index d830df3aa..ec943bf00 100644
--- a/virtinst/cloner.py
+++ b/virtinst/cloner.py
@@ -171,10 +171,7 @@ class Cloner(object):
 
     # MAC address for the new guest clone
     def set_clone_macs(self, mac):
-        maclist = xmlutil.listify(mac)
-        for m in maclist:
-            DeviceInterface.is_conflict_net(self.conn, m)
-        self._clone_macs = maclist
+        self._clone_macs = xmlutil.listify(mac)
     def get_clone_macs(self):
         return self._clone_macs
     clone_macs = property(get_clone_macs, set_clone_macs)
diff --git a/virtinst/devices/interface.py b/virtinst/devices/interface.py
index 02f756fc2..229f9a089 100644
--- a/virtinst/devices/interface.py
+++ b/virtinst/devices/interface.py
@@ -159,6 +159,9 @@ class DeviceInterface(Device):
         """
         Raise RuntimeError if the passed mac conflicts with a defined VM
         """
+        if not searchmac:
+            return
+
         vms = conn.fetch_all_domains()
         for vm in vms:
             for nic in vm.devices.interface:
@@ -252,12 +255,6 @@ class DeviceInterface(Device):
     # Build API #
     #############
 
-    def validate(self):
-        if not self.macaddr:
-            return
-
-        self.is_conflict_net(self.conn, self.macaddr)
-
     def set_default_source(self):
         if self.conn.is_qemu_unprivileged() or self.conn.is_test():
             self.type = self.TYPE_USER
diff --git a/virtinst/virtclone.py b/virtinst/virtclone.py
index 5f49d14f5..0dbd4d77d 100644
--- a/virtinst/virtclone.py
+++ b/virtinst/virtclone.py
@@ -51,6 +51,8 @@ def get_clone_macaddr(new_mac, design):
         return
     design.clone_macs = new_mac
 
+    for mac in design.clone_macs:
+        cli.validate_mac(design.conn, mac)
 
 
 def get_clone_diskfile(new_diskfiles, design, preserve, auto_clone):
diff --git a/virtinst/virtinstall.py b/virtinst/virtinstall.py
index fa9366fd1..08c091268 100644
--- a/virtinst/virtinstall.py
+++ b/virtinst/virtinstall.py
@@ -588,6 +588,8 @@ def build_guest_instance(conn, options):
         # cli specific disk validation
         for disk in guest.devices.disk:
             cli.validate_disk(disk)
+        for net in guest.devices.interface:
+            cli.validate_mac(net.conn, net.macaddr)
 
     validate_required_options(options, guest, installer)
     show_guest_warnings(options, guest, osdata)