diff --git a/models.py b/models.py
index e09c445..a71d5bd 100644
--- a/models.py
+++ b/models.py
@@ -53,10 +53,18 @@ class OpenHours(BaseModel):
     """Weekly opening schedule. Weekday key 0=Mon .. 6=Sun.
 
     Each day is a list of {start, end} ranges so a venue can be open
-    e.g. 11:00-15:00 and 18:00-23:00 in the same day.
+    e.g. 11:00-15:00 and 18:00-23:00 in the same day. Persisted as
+    JSON in the DB.
+
+    Typed as plain `dict` (not `dict[str, list[dict[str, str]]]`) so
+    LNbits's `db.dict_to_model` walks the field cleanly: its
+    introspection calls `issubclass(field.type_, bool)` while
+    iterating, and a parameterized generic alias trips it with
+    "issubclass() arg 1 must be a class". The runtime shape is
+    still the dict-of-lists-of-dicts described above.
     """
 
-    schedule: dict[str, list[dict[str, str]]] = Field(default_factory=dict)
+    schedule: dict = Field(default_factory=dict)
 
 
 class SocialLinks(BaseModel):
@@ -69,7 +77,10 @@ class SocialLinks(BaseModel):
 
 class RestaurantExtra(BaseModel):
     notes: Optional[str] = None
-    fields: dict[str, str] = Field(default_factory=dict)
+    # Typed as plain `dict` (not `dict[str, str]`) so LNbits's
+    # `db.dict_to_model` round-trips it cleanly — see OpenHours for
+    # the same workaround and rationale.
+    fields: dict = Field(default_factory=dict)
 
 
 class CreateRestaurant(BaseModel):
@@ -211,7 +222,8 @@ class MenuItemExtra(BaseModel):
     """Free-form metadata that doesn't deserve a column yet."""
 
     notes: Optional[str] = None
-    fields: dict[str, str] = Field(default_factory=dict)
+    # Plain `dict` — see OpenHours for the LNbits round-trip workaround.
+    fields: dict = Field(default_factory=dict)
 
 
 class CreateMenuItem(BaseModel):
@@ -404,7 +416,8 @@ class OrderExtra(BaseModel):
     fiat_currency: Optional[str] = None
     fiat_rate: Optional[float] = None
     refund_address: Optional[str] = None
-    fields: dict[str, str] = Field(default_factory=dict)
+    # Plain `dict` — see OpenHours for the LNbits round-trip workaround.
+    fields: dict = Field(default_factory=dict)
 
 
 class CreateOrder(BaseModel):