diff --git a/src/user-admin.c b/src/user-admin.c
index c51a2022..a4fb6941 100644
--- a/src/user-admin.c
+++ b/src/user-admin.c
@@ -23,8 +23,10 @@
 #include <pwd.h>
 #include <libintl.h>
 #include <locale.h>
+#include <glib.h>
 #include <glib/gi18n.h>
 #include <grp.h>
+#include <string.h>
 #include <sys/types.h>
 #include <libgroupservice/gas-group.h>
 #include <libgroupservice/gas-group-manager.h>
@@ -285,6 +287,51 @@ static gboolean UserNameValidCheck (const gchar *UserName, gchar **Message)
     valid = TRUE;
     if (!in_use && !empty && !home_use)
     {
+        /* Follow adduser(8) policy:
+         * Read NAME_REGEX from /etc/adduser.conf, compile an anchored regex,
+         * and require the username to fully match it. If unavailable or
+         * invalid, fall back to current Debian/Ubuntu default: ^[a-z][-a-z0-9_]*$
+         * (lowercase first char; then lowercase, digits, '-' and '_').
+         */
+        {
+            gchar *contents = NULL, *rx_s = NULL;
+            gsize len = 0;
+            const gchar *fallback = "^[a-z][-a-z0-9_]*$";
+            if (g_file_get_contents("/etc/adduser.conf", &contents, &len, NULL)) {
+                gchar **lines = g_strsplit(contents, "\n", -1);
+                for (gchar **p = lines; p && *p; ++p) {
+                    gchar *line = g_strstrip(*p);
+                    if (!line || !*line || line[0] == '#')
+                        continue;
+                    if (g_str_has_prefix(line, "NAME_REGEX")) {
+                        /* Accept forms like: NAME_REGEX="...pattern..." */
+                        gchar *q1 = strchr(line, '"');
+                        if (q1) {
+                            gchar *q2 = strrchr(q1 + 1, '"');
+                            if (q2 && q2 > q1 + 1)
+                                rx_s = g_strndup(q1 + 1, (gsize)(q2 - (q1 + 1)));
+                        }
+                        break;
+                    }
+                }
+                g_strfreev(lines);
+                g_free(contents);
+            }
+
+            GError *rx_err = NULL;
+            GRegex *rx = g_regex_new(rx_s ? rx_s : fallback, G_REGEX_ANCHORED, 0, &rx_err);
+            g_free(rx_s);
+            if (rx) {
+                if (!g_regex_match(rx, UserName, 0, NULL)) {
+                    valid = FALSE;
+                }
+                g_regex_unref(rx);
+            } else {
+                /* If regex cannot compile, be conservative */
+                if (rx_err) g_error_free(rx_err);
+                valid = FALSE;
+            }
+        }
         for (c = UserName; *c; c++)
         {
             if (! ((*c >= 'a' && *c <= 'z') ||
@@ -313,7 +360,7 @@ static gboolean UserNameValidCheck (const gchar *UserName, gchar **Message)
         }
         else
         {
-            *Message = g_strdup (_("The username should only consist of upper and lower case \nletters from a-z,digits and the following characters: . - _"));
+            *Message = g_strdup (_("The username first character must be lower case, use only \nlowercase letters (a–z), digits and the following characters: -_"));
         }
     }