diff --git a/CHANGES.rst b/CHANGES.rst
index 05e5acf29..279fd3f7d 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -6,6 +6,7 @@ Version 3.0.3
 Unreleased
 
 -   Make reloader more robust when ``""`` is in ``sys.path``. :pr:`2823`
+-   Better TLS cert format with ``adhoc`` dev certs. :pr:`2891`
 
 
 Version 3.0.2
diff --git a/src/werkzeug/serving.py b/src/werkzeug/serving.py
index ad6bf911b..7f6ea922e 100644
--- a/src/werkzeug/serving.py
+++ b/src/werkzeug/serving.py
@@ -532,7 +532,10 @@ def generate_adhoc_ssl_pair(
         .not_valid_before(dt.now(timezone.utc))
         .not_valid_after(dt.now(timezone.utc) + timedelta(days=365))
         .add_extension(x509.ExtendedKeyUsage([x509.OID_SERVER_AUTH]), critical=False)
-        .add_extension(x509.SubjectAlternativeName([x509.DNSName(cn)]), critical=False)
+        .add_extension(
+            x509.SubjectAlternativeName([x509.DNSName(cn), x509.DNSName(f"*.{cn}")]),
+            critical=False,
+        )
         .sign(pkey, hashes.SHA256(), backend)
     )
     return cert, pkey
@@ -560,7 +563,7 @@ def make_ssl_devcert(
     """
 
     if host is not None:
-        cn = f"*.{host}/CN={host}"
+        cn = host
     cert, pkey = generate_adhoc_ssl_pair(cn=cn)
 
     from cryptography.hazmat.primitives import serialization