diff --git a/src/zino/planned_maintenance.py b/src/zino/planned_maintenance.py
index af6543d90..252402bf1 100644
--- a/src/zino/planned_maintenance.py
+++ b/src/zino/planned_maintenance.py
@@ -1,10 +1,17 @@
 import logging
 from datetime import datetime, timedelta
-from typing import TYPE_CHECKING, Dict, Optional, Protocol
+from typing import TYPE_CHECKING, Dict, Optional, Protocol, Union
 
 from pydantic.main import BaseModel
 
-from zino.statemodels import Event, EventState, MatchType, PlannedMaintenance
+from zino.statemodels import (
+    DeviceMaintenance,
+    Event,
+    EventState,
+    MatchType,
+    PlannedMaintenance,
+    PortStateMaintenance,
+)
 
 if TYPE_CHECKING:
     from zino.state import ZinoState
@@ -22,7 +29,7 @@ def __call__(self) -> None: ...
 
 
 class PlannedMaintenances(BaseModel):
-    planned_maintenances: Dict[int, PlannedMaintenance] = {}
+    planned_maintenances: Dict[int, Union[DeviceMaintenance, PortStateMaintenance]] = {}
     last_pm_id: int = 0
     last_run: Optional[datetime] = datetime.fromtimestamp(0)
     _observers: list[PlannedMaintenanceObserver] = []
@@ -40,7 +47,7 @@ def create_planned_maintenance(
         pm_class: type[PlannedMaintenance],
         match_type: MatchType,
         match_expression: str,
-        match_device: Optional[str],
+        match_device: Optional[str] = None,
     ) -> PlannedMaintenance:
         """Creates a planned maintenance, adds it to the planned_maintenances dict and
         returns it
diff --git a/src/zino/statemodels.py b/src/zino/statemodels.py
index 06ab2997c..12070fa19 100644
--- a/src/zino/statemodels.py
+++ b/src/zino/statemodels.py
@@ -393,7 +393,7 @@ class PlannedMaintenance(BaseModel):
     end_time: datetime.datetime
     type: PmType
     match_type: MatchType
-    match_device: Optional[str]
+    match_device: Optional[str] = None
     match_expression: str
     log: List[LogEntry] = []
     event_ids: List[int] = []
@@ -430,7 +430,7 @@ def _get_or_create_events(self, state: "ZinoState") -> list[Event]:
 
 
 class DeviceMaintenance(PlannedMaintenance):
-    type: PmType = PmType.DEVICE
+    type: Literal[PmType.DEVICE] = PmType.DEVICE
 
     def matches_event(self, event: Event, state: "ZinoState") -> bool:
         """Returns true if `event` will be affected by this planned maintenance"""
@@ -470,7 +470,7 @@ def _get_or_create_events(self, state: "ZinoState") -> list[Event]:
 
 
 class PortStateMaintenance(PlannedMaintenance):
-    type: PmType = PmType.PORTSTATE
+    type: Literal[PmType.PORTSTATE] = PmType.PORTSTATE
 
     def matches_event(self, event: Event, state: "ZinoState") -> bool:
         """Returns true if `event` will be affected by this planned maintenance"""
diff --git a/tests/planned_maintenance_test.py b/tests/planned_maintenance_test.py
index 03306ae2e..eade9083c 100644
--- a/tests/planned_maintenance_test.py
+++ b/tests/planned_maintenance_test.py
@@ -148,6 +148,16 @@ def test_event_opened_after_pm_was_initiated_should_be_set_to_ignored(self, stat
         assert state.events.checkout(event.id).state == EventState.IGNORED
 
 
+def test_pms_should_be_parsed_as_correct_subclass_when_read_from_file(tmp_path, state, active_portstate_pm, active_pm):
+    dumpfile = tmp_path / "dump.json"
+    state.dump_state_to_file(dumpfile)
+    read_state = ZinoState.load_state_from_file(str(dumpfile))
+    read_device_pm = read_state.planned_maintenances[active_pm.id]
+    read_portstate_pm = read_state.planned_maintenances[active_portstate_pm.id]
+    assert isinstance(read_device_pm, DeviceMaintenance)
+    assert isinstance(read_portstate_pm, PortStateMaintenance)
+
+
 @pytest.fixture
 def pms():
     return PlannedMaintenances()