diff --git a/src/parsers/command-db-uri.lisp b/src/parsers/command-db-uri.lisp
index 8ada563..6c2b790 100644
--- a/src/parsers/command-db-uri.lisp
+++ b/src/parsers/command-db-uri.lisp
@@ -70,12 +70,42 @@
 		(declare (ignore unix))
     (list :unix (when socket-directory (text socket-directory)))))
 
-(defrule network-name (and namestring (* (and "." namestring)))
+;;;
+;;; See https://en.wikipedia.org/wiki/Hostname#Restrictions_on_valid_hostnames
+;;;
+;;; The characters allowed in labels are a subset of the ASCII character
+;;; set, consisting of characters a through z, A through Z, digits 0 through
+;;; 9, and hyphen.
+;;;
+;;; This rule is known as the LDH rule (letters, digits, hyphen).
+;;;
+;;;  - Domain names are interpreted in case-independent manner.
+;;;  - Labels may not start or end with a hyphen.
+;;;  - An additional rule requires that top-level domain names should not be
+;;;    all-numeric.
+;;;
+(defrule network-label-letters-digit (or (alpha-char-p character)
+                                         (digit-char-p character)))
+
+(defrule network-label-with-hyphen
+    (and network-label-letters-digit
+         (+ (or (and #\- (& network-label-letters-digit))
+                network-label-letters-digit))
+         (! #\-))
+  (:text t))
+
+(defrule network-label-no-hyphen (+ network-label-letters-digit)
+  (:text t))
+
+(defrule network-label (or network-label-with-hyphen network-label-no-hyphen)
+  (:identity t))
+
+(defrule network-hostname (and network-label (* (and "." network-label)))
   (:lambda (name)
     (let ((host (text name)))
       (list :host (unless (string= "" host) host)))))
 
-(defrule hostname (or ipv4 ipv6 socket-directory network-name)
+(defrule hostname (or ipv4 ipv6 socket-directory network-hostname)
   (:identity t))
 
 (defun process-hostname (hostname)