diff --git a/pcapkit/const/ipv4/qs_function.py b/pcapkit/const/ipv4/qs_function.py
index 1ba0fa2c03..2bb798c4e8 100644
--- a/pcapkit/const/ipv4/qs_function.py
+++ b/pcapkit/const/ipv4/qs_function.py
@@ -32,6 +32,6 @@ def _missing_(cls, value: 'int') -> 'QSFunction':
             value: Value to get enum item.
 
         """
-        if not (isinstance(value, int) and 0 <= value <= 8):
+        if not (isinstance(value, int) and 0 <= value <= 15):
             raise ValueError('%r is not a valid %s' % (value, cls.__name__))
         return cls._unregistered_member(value, 'Unassigned')
diff --git a/pcapkit/const/ipv6/qs_function.py b/pcapkit/const/ipv6/qs_function.py
index 9ed321d0aa..caf2ab9b5d 100644
--- a/pcapkit/const/ipv6/qs_function.py
+++ b/pcapkit/const/ipv6/qs_function.py
@@ -32,6 +32,6 @@ def _missing_(cls, value: 'int') -> 'QSFunction':
             value: Value to get enum item.
 
         """
-        if not (isinstance(value, int) and 0 <= value <= 8):
+        if not (isinstance(value, int) and 0 <= value <= 15):
             raise ValueError('%r is not a valid %s' % (value, cls.__name__))
         return cls._unregistered_member(value, 'Unassigned')
diff --git a/pcapkit/vendor/ipv4/qs_function.py b/pcapkit/vendor/ipv4/qs_function.py
index ea199cfa52..b8d8edf6a9 100644
--- a/pcapkit/vendor/ipv4/qs_function.py
+++ b/pcapkit/vendor/ipv4/qs_function.py
@@ -31,7 +31,7 @@ class QSFunction(Vendor):
     """QS Functions"""
 
     #: Value limit checker.
-    FLAG = 'isinstance(value, int) and 0 <= value <= 8'
+    FLAG = 'isinstance(value, int) and 0 <= value <= 15'
 
     def request(self) -> 'dict[int, str]':  # type: ignore[override] # pylint: disable=arguments-differ
         """Fetch registry data.
diff --git a/pcapkit/vendor/ipv6/qs_function.py b/pcapkit/vendor/ipv6/qs_function.py
index 4a46284333..90a8d4bb00 100644
--- a/pcapkit/vendor/ipv6/qs_function.py
+++ b/pcapkit/vendor/ipv6/qs_function.py
@@ -31,7 +31,7 @@ class QSFunction(Vendor):
     """QS Functions"""
 
     #: Value limit checker.
-    FLAG = 'isinstance(value, int) and 0 <= value <= 8'
+    FLAG = 'isinstance(value, int) and 0 <= value <= 15'
 
     def request(self) -> 'dict[int, str]':  # type: ignore[override] # pylint: disable=arguments-differ
         """Fetch registry data.
diff --git a/tests/const/test_const_qs_function_range_unit.py b/tests/const/test_const_qs_function_range_unit.py
new file mode 100644
index 0000000000..745afa27b9
--- /dev/null
+++ b/tests/const/test_const_qs_function_range_unit.py
@@ -0,0 +1,73 @@
+# -*- coding: utf-8 -*-
+"""The Quick-Start ``QSFunction`` enums accept the whole four-bit field.
+
+GitHub issue #1350: RFC 4782 section 3.1 gives the Quick-Start option "a
+four-bit Function field", so every value in ``0..15`` is a valid wire value,
+and those without an assignment (``1..7`` and ``9..15``) resolve to an
+``Unassigned`` member. Values outside the field are still rejected.
+
+The bound comes from ``FLAG`` in the vendor templates
+:mod:`pcapkit.vendor.ipv4.qs_function` and :mod:`pcapkit.vendor.ipv6.qs_function`,
+so the generated const files are also checked against the template's output.
+Both templates take their registry from a local ``DATA`` dict, so rendering
+them reaches no network.
+
+Modules are imported inside each test, after
+:func:`~tests._support.reimport_once_per_class`, not at module load.
+
+"""
+
+import importlib
+import os
+import tempfile
+import unittest
+from unittest import mock
+
+from tests._support import reimport_once_per_class
+
+NAMESPACES = ('ipv4', 'ipv6')
+
+
+class TestQSFunctionRange(unittest.TestCase):
+    """Pin the accepted range of both ``QSFunction`` enums."""
+
+    def setUp(self) -> None:
+        reimport_once_per_class(self)
+
+    def test_unassigned_values_resolve(self) -> None:
+        for ns in NAMESPACES:
+            enum = importlib.import_module(f'pcapkit.const.{ns}.qs_function').QSFunction
+            for value in range(16):
+                with self.subTest(ns=ns, value=value):
+                    member = enum.get(value)
+                    self.assertEqual(int(member), value)
+                    if value not in (0, 8):
+                        self.assertEqual(enum(value), member)
+                        self.assertTrue(member.name.startswith('Unassigned'), member.name)
+
+    def test_values_outside_the_field_are_rejected(self) -> None:
+        for ns in NAMESPACES:
+            enum = importlib.import_module(f'pcapkit.const.{ns}.qs_function').QSFunction
+            for value in (-1, 16, 255):
+                with self.subTest(ns=ns, value=value):
+                    with self.assertRaises(ValueError):
+                        enum(value)
+
+    def test_const_file_matches_template_output(self) -> None:
+        for ns in NAMESPACES:
+            with self.subTest(ns=ns):
+                vendor = importlib.import_module(f'pcapkit.vendor.{ns}.qs_function').QSFunction
+                self.assertIsNone(vendor.LINK)
+                const_file = vendor._dest_path()
+                with tempfile.TemporaryDirectory() as tempdir:
+                    dest = os.path.join(tempdir, 'qs_function.py')
+                    with mock.patch.object(vendor, '_dest_path', return_value=dest):
+                        vendor()
+                    with open(dest, 'rb') as file:
+                        rendered = file.read()
+                with open(const_file, 'rb') as file:
+                    self.assertEqual(file.read(), rendered)
+
+
+if __name__ == '__main__':
+    unittest.main()