diff --git a/networks/templates/modify_ipv4_fixed_address.html b/networks/templates/modify_ipv4_fixed_address.html
index 05bf1ff9..4886e0bc 100644
--- a/networks/templates/modify_ipv4_fixed_address.html
+++ b/networks/templates/modify_ipv4_fixed_address.html
@@ -24,13 +24,13 @@
                     <div class="row">
                         <label class="col-sm-4 col-form-label">{% trans "MAC" %}</label>
                         <div class="col-sm-6">
-                            <input type="text" class="form-control" name="mac" required pattern="[0-9\/\:]+">
+                            <input type="text" class="form-control" name="mac" required pattern="[0-9a-fA-F:]+">
                         </div>
                     </div>
                     <div class="row">
                         <label class="col-sm-4 col-form-label">{% trans "Name" %}</label>
                         <div class="col-sm-6">
-                            <input type="text" class="form-control" name="name" pattern="[a-zA-Z0-9_]+">
+                            <input type="text" class="form-control" name="name" pattern="[a-zA-Z0-9_.\-]+">
                         </div>
                     </div>
                     <div class="row">
diff --git a/networks/templates/modify_ipv6_fixed_address.html b/networks/templates/modify_ipv6_fixed_address.html
index e5439bda..4ca340bc 100644
--- a/networks/templates/modify_ipv6_fixed_address.html
+++ b/networks/templates/modify_ipv6_fixed_address.html
@@ -30,7 +30,7 @@
                     <div class="row">
                         <label class="col-sm-4 col-form-label">{% trans "Name" %}</label>
                         <div class="col-sm-6">
-                            <input type="text" class="form-control" name="name" pattern="[a-zA-Z0-9_]+">
+                            <input type="text" class="form-control" name="name" pattern="[a-zA-Z0-9_.\-]+">
                         </div>
                     </div>
                     <div class="row">
diff --git a/networks/tests/__init__.py b/networks/tests/__init__.py
new file mode 100644
index 00000000..e69de29b
diff --git a/networks/tests/test_fixed_address_form.py b/networks/tests/test_fixed_address_form.py
new file mode 100644
index 00000000..3f92317a
--- /dev/null
+++ b/networks/tests/test_fixed_address_form.py
@@ -0,0 +1,31 @@
+"""The fixed-address dialogs take real MAC addresses and host names: the
+browser refuses what their pattern attributes do not match."""
+
+import re
+from types import SimpleNamespace
+
+from django.template.loader import render_to_string
+from django.test import SimpleTestCase
+from lxml import html
+
+
+def pattern(template, name):
+    superuser = SimpleNamespace(user=SimpleNamespace(is_superuser=True))
+    page = html.fromstring(render_to_string(template, {"request": superuser}))
+    return re.compile(page.xpath(f"//input[@name='{name}']/@pattern")[0])
+
+
+class FixedAddressFormTests(SimpleTestCase):
+    def test_macs_and_host_names_are_accepted(self):
+        mac = pattern("modify_ipv4_fixed_address.html", "mac")
+        for value in ("52:54:00:ab:cd:ef", "52:54:00:AB:CD:EF"):
+            with self.subTest(mac=value):
+                self.assertTrue(mac.fullmatch(value))
+        for template in ("modify_ipv4_fixed_address.html", "modify_ipv6_fixed_address.html"):
+            name = pattern(template, "name")
+            for value in ("web-01", "db.lan", "vm_1"):
+                with self.subTest(template=template, name=value):
+                    self.assertTrue(name.fullmatch(value))
+            for value in ("a b", 'x"<'):
+                with self.subTest(template=template, refused=value):
+                    self.assertFalse(name.fullmatch(value))