diff --git a/tests/application/test_startup.py b/tests/application/test_startup.py
index 8394a86..8211bc9 100644
--- a/tests/application/test_startup.py
+++ b/tests/application/test_startup.py
@@ -313,3 +313,42 @@ async def test_concurrency_auto_config(device, concurrency, make_application):
     await app.start_network()
 
     assert app._concurrent_requests_semaphore.max_concurrency == concurrency
+
+
+@pytest.mark.parametrize(
+    ("code_revision", "expected"),
+    [
+        (None, False),
+        (20190608, False),
+        (20221226, False),
+        (20230506, False),
+        (20230507, True),
+        (20250321, True),
+    ],
+)
+async def test_child_aging_by_build(code_revision, expected, make_application):
+    app, znp_server = make_application(FormedLaunchpadCC26X2R1)
+
+    znp_server.reply_to(
+        c.SYS.Version.Req(),
+        responses=c.SYS.Version.Rsp(
+            TransportRev=2,
+            ProductId=1,
+            MajorRel=2,
+            MinorRel=7,
+            MaintRel=1,
+            CodeRevision=code_revision,
+            BootloaderBuildType=None,
+            BootloaderRevision=None,
+        ),
+        override=True,
+    )
+
+    await app.startup(auto_form=False)
+
+    value = await app._znp.nvram.osal_read(
+        OsalNvIds.NWK_CHILD_AGE_ENABLE, item_type=t.Bool
+    )
+    assert value == expected
+
+    await app.shutdown()
diff --git a/zigpy_znp/zigbee/application.py b/zigpy_znp/zigbee/application.py
index be95a9a..30f33e4 100644
--- a/zigpy_znp/zigbee/application.py
+++ b/zigpy_znp/zigbee/application.py
@@ -36,6 +36,8 @@
 DATA_CONFIRM_TIMEOUT = 8
 EXTENDED_DATA_CONFIRM_TIMEOUT = 30
 DEVICE_JOIN_MAX_DELAY = 5
+# First Koenkk Z-Stack 3.x.0 build with child aging enabled (and Xiaomi exempted)
+CHILD_AGING_MIN_BUILD_ID = 20230507
 
 LOGGER = logging.getLogger(__name__)
 
@@ -139,6 +141,9 @@ async def start_network(self, *, read_only=False):
         if self.state.node_info == zigpy.state.NodeInfo():
             await self.load_network_info()
 
+        # Needed by the stack settings below
+        self._version_rsp = await self._znp.request(c.SYS.Version.Req())
+
         if not read_only:
             await self._znp.migrate_nvram()
             await self._write_stack_settings()
@@ -150,8 +155,6 @@ async def start_network(self, *, read_only=False):
 
         await self._znp.start_network()
 
-        self._version_rsp = await self._znp.request(c.SYS.Version.Req())
-
         # The CC2531 running Z-Stack Home 1.2 overrides the LED setting if it is changed
         # before the coordinator has started.
         if self.znp_config[conf.CONF_LED_MODE] is not None:
@@ -624,7 +627,13 @@ async def _write_stack_settings(self) -> bool:
             OsalNvIds.CONCENTRATOR_DISCOVERY: t.uint8_t(120),
             OsalNvIds.CONCENTRATOR_RC: t.Bool(True),
             OsalNvIds.SRC_RTG_EXPIRY_TIME: t.uint8_t(255),
-            OsalNvIds.NWK_CHILD_AGE_ENABLE: t.Bool(False),
+            # Koenkk's builds enable child aging from 20230507 on and skip the leave
+            # for Xiaomi devices, which do not implement it. Older builds have no such
+            # exception, so aging stays off there. The value is written either way
+            # because an earlier zigpy-znp may have left `False` in NVRAM.
+            OsalNvIds.NWK_CHILD_AGE_ENABLE: t.Bool(
+                self._zstack_build_id >= CHILD_AGING_MIN_BUILD_ID
+            ),
             # Default is 20 in Z-Stack 3.0.1, 30 in Z-Stack 3/4
             OsalNvIds.BCAST_DELIVERY_TIME: t.uint8_t(30),
             # We want to receive all ZDO callbacks to proxy them back to zigpy
@@ -936,10 +945,10 @@ async def send_packet(self, packet: zigpy.types.ZigbeePacket) -> None:
                     except InvalidCommandResponse as e:
                         last_error = e
 
-                        # Child aging is disabled so if a child switches parents from
-                        # the coordinator to another router, we will not be able to
-                        # re-discover a route to it. We have to manually drop the child
-                        # to do this.
+                        # Child aging is off on older builds, so if a child switches
+                        # parents from the coordinator to another router, we will not be
+                        # able to re-discover a route to it. We have to manually drop
+                        # the child to do this.
                         if (
                             e.response.Status == t.Status.MAC_TRANSACTION_EXPIRED
                             and device is not None