diff --git a/lemur/dns_providers/util.py b/lemur/dns_providers/util.py
index 9aa10458..fc930eb3 100644
--- a/lemur/dns_providers/util.py
+++ b/lemur/dns_providers/util.py
@@ -35,7 +35,7 @@ def is_valid_domain(domain):
         domain = domain[:-1]
     if len(domain) > 253:
         return False
-    fqdn_re = re.compile("(?=^.{1,63}$)(^(?:[a-z0-9](?:-*[a-z0-9])+)$)", re.IGNORECASE)
+    fqdn_re = re.compile("(?=^.{1,63}$)(^(?:[a-z0-9](?:-*[a-z0-9])+)|[a-z0-9]$)", re.IGNORECASE)
     return all(fqdn_re.match(d) for d in domain.split("."))
 
 
diff --git a/lemur/tests/test_dns_providers.py b/lemur/tests/test_dns_providers.py
index b8714a2d..640277c6 100644
--- a/lemur/tests/test_dns_providers.py
+++ b/lemur/tests/test_dns_providers.py
@@ -6,7 +6,18 @@ class TestDNSProvider(unittest.TestCase):
     def test_is_valid_domain(self):
         self.assertTrue(dnsutil.is_valid_domain("example.com"))
         self.assertTrue(dnsutil.is_valid_domain("foo.bar.org"))
-        self.assertTrue(dnsutil.is_valid_domain("_acme-chall.example.com"))
+        self.assertTrue(dnsutil.is_valid_domain("exam--ple.io"))
+        self.assertTrue(dnsutil.is_valid_domain("a.example.com"))
+        self.assertTrue(dnsutil.is_valid_domain("example.io"))
+        self.assertTrue(dnsutil.is_valid_domain("example-of-63-character-domain-label-length-limit-1234567890123.com"))
+        self.assertFalse(dnsutil.is_valid_domain("example-of-63-character-domain-label-length-limit-12345678901234.com"))
+        self.assertFalse(dnsutil.is_valid_domain("_acme-chall.example.com"))
         self.assertFalse(dnsutil.is_valid_domain("e/xample.com"))
         self.assertFalse(dnsutil.is_valid_domain("exam\ple.com"))
         self.assertFalse(dnsutil.is_valid_domain("*.example.com"))
+        self.assertFalse(dnsutil.is_valid_domain("-example.io"))
+        self.assertFalse(dnsutil.is_valid_domain("example-.io"))
+        self.assertFalse(dnsutil.is_valid_domain("example..io"))
+        self.assertFalse(dnsutil.is_valid_domain("exa mple.io"))
+        self.assertFalse(dnsutil.is_valid_domain("-"))
+        self.assertFalse(dnsutil.is_valid_domain(""))