diff --git a/djangorota/rota/models.py b/djangorota/rota/models.py
index e3bac1f..e738f37 100644
--- a/djangorota/rota/models.py
+++ b/djangorota/rota/models.py
@@ -171,6 +171,83 @@ class Worker(models.Model):
 			if isinstance(opts, dict):
 				# shallow merge; keys in `options` override defaults above when present
 				pyd_kwargs.update(opts)
+
+				# Defensive normalization: the DB may contain `null`/`[]` for fields
+				# that the pydantic model expects to be ints/dicts/lists. Coerce a
+				# few common keys to safe defaults so Worker(**kwargs) doesn't raise
+				# on older or malformed records.
+				int_keys = [
+					"locum_max_shifts",
+					"locum_max_shifts_per_week",
+					"bank_holiday_extra",
+					"prefer_multi_shift_together",
+					"weekend_shift_target_number",
+				]
+				dict_keys = [
+					"previous_shifts",
+					"shift_balance_extra",
+					"force_assign_with",
+					"max_shifts_per_week_by_shift_name",
+					"assign_as_block_preferences",
+					"shift_fte_overrides",
+				]
+				list_keys = [
+					"oop",
+					"not_available_to_work",
+					"pref_not_to_work",
+					"work_requests",
+					"locum_availability",
+					"allowed_multi_shift_sets",
+					"hard_day_dependencies",
+					"hard_day_exclusions",
+					"forced_assignments",
+					"forced_assignments_by_date",
+				]
+
+				for k in int_keys:
+					v = pyd_kwargs.get(k, None)
+					try:
+						if v is None:
+							pyd_kwargs[k] = 0
+						else:
+							pyd_kwargs[k] = int(v)
+					except Exception:
+						pyd_kwargs[k] = 0
+
+				for k in dict_keys:
+					v = pyd_kwargs.get(k, None)
+					if not isinstance(v, dict):
+						# If a list was stored accidentally (common migration/serialization
+						# mistakes) coerce to an empty dict rather than letting pydantic
+						# fail.
+						pyd_kwargs[k] = {}
+
+				for k in list_keys:
+					v = pyd_kwargs.get(k, None)
+					if v is None:
+						pyd_kwargs[k] = []
+					elif isinstance(v, list):
+						# leave as-is
+						pass
+					elif isinstance(v, (set, tuple)):
+						pyd_kwargs[k] = list(v)
+					else:
+						pyd_kwargs[k] = []
+
+				# allowed_multi_shift_sets is expected to be a list of sets; if the
+				# DB contains lists-of-lists convert inner lists to sets.
+				ams = pyd_kwargs.get("allowed_multi_shift_sets")
+				if isinstance(ams, list):
+					new = []
+					for item in ams:
+						if isinstance(item, list):
+							new.append(set(item))
+						elif isinstance(item, (set, tuple)):
+							new.append(set(item))
+						else:
+							# leave unknown types to pydantic to either accept or coerce
+							new.append(item)
+					pyd_kwargs["allowed_multi_shift_sets"] = new
 		except Exception:
 			# ignore any issues reading options and proceed with core fields
 			pass