diff --git a/letsencrypt/cli.py b/letsencrypt/cli.py
index 1f04ee173..c66060d48 100644
--- a/letsencrypt/cli.py
+++ b/letsencrypt/cli.py
@@ -1152,17 +1152,29 @@ def check_config_sanity(args):
     """
     # Domain checks
     if args.domains is not None:
-        # Check if there's a wildcard domain
-        if any(d.startswith("*.") for d in args.domains):
-            raise errors.ConfigurationError("Error: Wildcard domains are not supported")
-        # Punycode
-        if any("xn--" in d for d in args.domains):
-            raise errors.ConfigurationError("Error: Punycode domains are not supported")
-        # FQDN, checks:
-        #  Characters used, domain parts < 63 chars, tld > 3 < 6 chars
-        fqdn = re.compile("^((?!-)[A-Za-z0-9-]{1,63}(?<!-)\\.)+[A-Za-z]{2,6}$")
-        if any(True for d in args.domains if not fqdn.match(d)):
-            raise errors.ConfigurationError("Error: Requested domain is not FQDN")
+        _check_config_domain_sanity(args.domains)
+
+def _check_config_domain_sanity(domains):
+    """Helper method for check_config_sanity which validates
+    domain flag values and errors out if the requirements are not met.
+
+    :param domains: List of domains
+    :type args: `list` of `string`
+
+    """
+    # Check if there's a wildcard domain
+    if any(d.startswith("*.") for d in domains):
+        raise errors.ConfigurationError(
+            "Error: Wildcard domains are not supported")
+    # Punycode
+    if any("xn--" in d for d in domains):
+        raise errors.ConfigurationError(
+            "Error: Punycode domains are not supported")
+    # FQDN, checks:
+    #  Characters used, domain parts < 63 chars, tld > 3 < 6 chars
+    fqdn = re.compile("^((?!-)[A-Za-z0-9-]{1,63}(?<!-)\\.)+[A-Za-z]{2,6}$")
+    if any(True for d in domains if not fqdn.match(d)):
+        raise errors.ConfigurationError("Error: Requested domain is not FQDN")
 
 if __name__ == "__main__":
     err_string = main()