diff --git a/app/dependencies/filter.py b/app/dependencies/filter.py
new file mode 100644
index 000000000..66acc4675
--- /dev/null
+++ b/app/dependencies/filter.py
@@ -0,0 +1,55 @@
+from copy import deepcopy
+from typing import Any, get_args, get_origin
+
+from fastapi import Depends, Query, params
+from fastapi.exceptions import RequestValidationError
+from fastapi_filter.base.filter import BaseFilterModel
+from pydantic import ValidationError, create_model
+
+
+def _list_to_query_fields(filter_model: type[BaseFilterModel]):
+    fields = {}
+    for name, f in filter_model.model_fields.items():
+        field_info = deepcopy(f)
+        annotation = f.annotation
+
+        if (
+            annotation is list
+            or get_origin(annotation) is list
+            or any(get_origin(a) is list for a in get_args(annotation))
+        ) and type(field_info.default) is not params.Query:
+            field_info.default = Query(default=field_info.default)
+
+        fields[name] = (f.annotation, field_info)
+
+    return fields
+
+
+def FilterDepends(filter_model: type[BaseFilterModel], *, by_alias: bool = False, **_) -> Any:
+    """Use a hack to treat lists as query parameters.
+
+    What we do is loop through the fields of a filter and assign any `list` field a default value of
+    `Query` so that FastAPI knows it should be treated a query parameter and not body.
+
+    When we apply the filter, we build the original filter to properly validate the data (i.e. can
+    the string be parsed and formatted as a list of <type>?)
+    """
+    fields = _list_to_query_fields(filter_model)
+    GeneratedFilter = create_model(filter_model.__class__.__name__, **fields)  # noqa: N806
+
+    class FilterWrapper(GeneratedFilter):  # type: ignore[misc,valid-type]
+        def __new__(cls, *args, **kwargs):
+            try:
+                instance = GeneratedFilter(*args, **kwargs)
+                data = instance.model_dump(
+                    exclude_unset=True, exclude_defaults=True, by_alias=by_alias
+                )
+                if original_filter := getattr(filter_model.Constants, "original_filter", None):
+                    prefix = f"{filter_model.Constants.prefix}__"
+                    stripped = {k.removeprefix(prefix): v for k, v in data.items()}
+                    return original_filter(**stripped)
+                return filter_model(**data)
+            except ValidationError as e:
+                raise RequestValidationError(e.errors()) from e
+
+    return Depends(FilterWrapper)
diff --git a/app/filters/activity.py b/app/filters/activity.py
index cf4806e86..8b039a896 100644
--- a/app/filters/activity.py
+++ b/app/filters/activity.py
@@ -1,8 +1,9 @@
 from datetime import datetime
 from typing import Annotated
 
-from fastapi_filter import FilterDepends, with_prefix
+from fastapi_filter import with_prefix
 
+from app.dependencies.filter import FilterDepends
 from app.filters.common import (
     CreationFilterMixin,
     CreatorFilterMixin,
diff --git a/app/filters/base.py b/app/filters/base.py
index a7747ee06..d32744fcd 100644
--- a/app/filters/base.py
+++ b/app/filters/base.py
@@ -8,6 +8,7 @@
 from sqlalchemy.orm import DeclarativeBase
 
 from app.db.model import Identifiable
+from app.logger import L
 
 Aliases = dict[type[Identifiable], type[Identifiable] | dict[str, type[Identifiable]]]
 
@@ -18,6 +19,33 @@ class CustomFilter[T: DeclarativeBase](Filter):
     class Constants(Filter.Constants):
         ordering_model_fields: list[str]
 
+    @field_validator("*", mode="before")
+    @classmethod
+    def split_str(cls, value, field):  # pyright: ignore reportIncompatibleMethodOverride
+        """Prevent splitting field logic from parent class."""
+        # backwards compatibility by splitting only comma separated single list elements that do not
+        # have space directly after the comma. e.g "a,b,c" will be split but not 'a, b, c'.
+        if (
+            field.field_name is not None  # noqa: PLR0916
+            and (
+                field.field_name == cls.Constants.ordering_field_name
+                or field.field_name.endswith("__in")
+                or field.field_name.endswith("__not_in")
+            )
+            and value
+            and len(value) == 1
+            and isinstance(value[0], str)
+            and "," in value[0]
+            and ", " not in value[0]
+        ):
+            msg = (
+                "Deprecated comma separated single-string IN query used instead of native list. "
+                f"Filter: field.config['title'] Field name: {field.field_name} Value: {value}"
+            )
+            L.warning(msg)
+            return value[0].split(",")
+        return value
+
     @field_validator("order_by", check_fields=False)
     @classmethod
     def restrict_sortable_fields(cls, value: list[str]):
diff --git a/app/filters/brain_atlas.py b/app/filters/brain_atlas.py
index 89d51a985..aca331356 100644
--- a/app/filters/brain_atlas.py
+++ b/app/filters/brain_atlas.py
@@ -1,8 +1,7 @@
 from typing import Annotated
 
-from fastapi_filter import FilterDepends
-
 from app.db.model import BrainAtlas, BrainAtlasRegion
+from app.dependencies.filter import FilterDepends
 from app.filters.base import CustomFilter
 from app.filters.common import IdFilterMixin, NameFilterMixin, SpeciesFilterMixin
 
diff --git a/app/filters/brain_region.py b/app/filters/brain_region.py
index 1b0728949..09879b204 100644
--- a/app/filters/brain_region.py
+++ b/app/filters/brain_region.py
@@ -2,10 +2,10 @@
 from typing import Annotated
 
 import sqlalchemy as sa
-from fastapi_filter import FilterDepends
 from sqlalchemy.orm import aliased
 
 from app.db.model import BrainRegion, BrainRegionHierarchy
+from app.dependencies.filter import FilterDepends
 from app.filters.base import CustomFilter
 from app.filters.common import NameFilterMixin
 
diff --git a/app/filters/brain_region_hierarchy.py b/app/filters/brain_region_hierarchy.py
index 33c19f209..0a6bafd68 100644
--- a/app/filters/brain_region_hierarchy.py
+++ b/app/filters/brain_region_hierarchy.py
@@ -1,8 +1,7 @@
 from typing import Annotated
 
-from fastapi_filter import FilterDepends
-
 from app.db.model import BrainRegionHierarchy
+from app.dependencies.filter import FilterDepends
 from app.filters.base import CustomFilter
 from app.filters.common import IdFilterMixin, NameFilterMixin
 
diff --git a/app/filters/cell_composition.py b/app/filters/cell_composition.py
index d9e443f0a..348e01e39 100644
--- a/app/filters/cell_composition.py
+++ b/app/filters/cell_composition.py
@@ -1,8 +1,7 @@
 from typing import Annotated
 
-from fastapi_filter import FilterDepends
-
 from app.db.model import CellComposition
+from app.dependencies.filter import FilterDepends
 from app.filters.base import CustomFilter
 from app.filters.common import (
     EntityFilterMixin,
diff --git a/app/filters/circuit.py b/app/filters/circuit.py
index 44eb1afca..27156d350 100644
--- a/app/filters/circuit.py
+++ b/app/filters/circuit.py
@@ -2,9 +2,8 @@
 from datetime import datetime
 from typing import Annotated
 
-from fastapi_filter import FilterDepends
-
 from app.db.model import Circuit
+from app.dependencies.filter import FilterDepends
 from app.filters.base import CustomFilter
 from app.filters.common import (
     BrainRegionFilterMixin,
diff --git a/app/filters/common.py b/app/filters/common.py
index 896d40b75..46538c431 100644
--- a/app/filters/common.py
+++ b/app/filters/common.py
@@ -2,7 +2,7 @@
 from datetime import datetime
 from typing import Annotated
 
-from fastapi_filter import FilterDepends, with_prefix
+from fastapi_filter import with_prefix
 
 from app.db.model import (
     Agent,
@@ -15,12 +15,17 @@
     Strain,
     Subject,
 )
+from app.dependencies.filter import FilterDepends
 from app.filters.base import CustomFilter
 
 
 class IdFilterMixin:
     id: uuid.UUID | None = None
-    id__in: list[uuid.UUID] | None = None
+
+    # id__in needs to be a str for backwards compatibility when instead of a native list a comma
+    # separated string is provided, e.g. 'id1,id2' . With list[UUID] backwards compatibility would
+    # fail because of validation of the field which would be expected to be a UUID.
+    id__in: list[str] | None = None
 
 
 class NameFilterMixin:
diff --git a/app/filters/density.py b/app/filters/density.py
index 0d2a91efa..25fcb1953 100644
--- a/app/filters/density.py
+++ b/app/filters/density.py
@@ -1,12 +1,11 @@
 from typing import Annotated
 
-from fastapi_filter import FilterDepends
-
 from app.db.model import (
     ExperimentalBoutonDensity,
     ExperimentalNeuronDensity,
     ExperimentalSynapsesPerConnection,
 )
+from app.dependencies.filter import FilterDepends
 from app.filters.base import CustomFilter
 from app.filters.common import (
     BrainRegionFilter,
diff --git a/app/filters/electrical_cell_recording.py b/app/filters/electrical_cell_recording.py
index e50694008..49405b007 100644
--- a/app/filters/electrical_cell_recording.py
+++ b/app/filters/electrical_cell_recording.py
@@ -1,8 +1,7 @@
 from typing import Annotated
 
-from fastapi_filter import FilterDepends
-
 from app.db.model import ElectricalCellRecording
+from app.dependencies.filter import FilterDepends
 from app.filters.base import CustomFilter
 from app.filters.common import (
     BrainRegionFilterMixin,
diff --git a/app/filters/emodel.py b/app/filters/emodel.py
index edcd970e7..0e4422e24 100644
--- a/app/filters/emodel.py
+++ b/app/filters/emodel.py
@@ -1,8 +1,9 @@
 from typing import Annotated
 
-from fastapi_filter import FilterDepends, with_prefix
+from fastapi_filter import with_prefix
 
 from app.db.model import EModel
+from app.dependencies.filter import FilterDepends
 from app.filters.base import CustomFilter
 from app.filters.common import (
     BrainRegionFilterMixin,
diff --git a/app/filters/entity.py b/app/filters/entity.py
index 066ac67aa..024864b2c 100644
--- a/app/filters/entity.py
+++ b/app/filters/entity.py
@@ -1,9 +1,8 @@
 from typing import Annotated
 
-from fastapi_filter import FilterDepends
-
 from app.db.model import Entity
 from app.db.types import EntityType
+from app.dependencies.filter import FilterDepends
 from app.filters.base import CustomFilter
 
 
diff --git a/app/filters/ion_channel_model.py b/app/filters/ion_channel_model.py
index 682072f80..310f166a7 100644
--- a/app/filters/ion_channel_model.py
+++ b/app/filters/ion_channel_model.py
@@ -1,8 +1,7 @@
 from typing import Annotated
 
-from fastapi_filter import FilterDepends
-
 from app.db.model import IonChannelModel
+from app.dependencies.filter import FilterDepends
 from app.filters.base import CustomFilter
 from app.filters.common import (
     BrainRegionFilterMixin,
diff --git a/app/filters/measurement_annotation.py b/app/filters/measurement_annotation.py
index 97d4c4613..e55d46e6c 100644
--- a/app/filters/measurement_annotation.py
+++ b/app/filters/measurement_annotation.py
@@ -1,11 +1,12 @@
 import uuid
 from typing import Annotated
 
-from fastapi_filter import FilterDepends, with_prefix
+from fastapi_filter import with_prefix
 
 from app.db.model import MeasurementAnnotation, MeasurementItem, MeasurementKind
 from app.db.types import MeasurementStatistic, MeasurementUnit, StructuralDomain
 from app.db.utils import MeasurableEntityType
+from app.dependencies.filter import FilterDepends
 from app.filters.base import CustomFilter
 from app.filters.common import CreationFilterMixin
 
diff --git a/app/filters/memodel.py b/app/filters/memodel.py
index bdc0089d9..5594f1d40 100644
--- a/app/filters/memodel.py
+++ b/app/filters/memodel.py
@@ -1,8 +1,9 @@
 from typing import Annotated
 
-from fastapi_filter import FilterDepends, with_prefix
+from fastapi_filter import with_prefix
 
 from app.db.model import MEModel, ValidationStatus
+from app.dependencies.filter import FilterDepends
 from app.filters.base import CustomFilter
 from app.filters.common import (
     BrainRegionFilterMixin,
diff --git a/app/filters/memodel_calibration_result.py b/app/filters/memodel_calibration_result.py
index 3fc629746..0358c0063 100644
--- a/app/filters/memodel_calibration_result.py
+++ b/app/filters/memodel_calibration_result.py
@@ -1,9 +1,8 @@
 import uuid
 from typing import Annotated
 
-from fastapi_filter import FilterDepends
-
 from app.db.model import MEModelCalibrationResult
+from app.dependencies.filter import FilterDepends
 from app.filters.base import CustomFilter
 from app.filters.common import EntityFilterMixin
 
diff --git a/app/filters/morphology.py b/app/filters/morphology.py
index 2853486e3..a4ffd947d 100644
--- a/app/filters/morphology.py
+++ b/app/filters/morphology.py
@@ -1,8 +1,9 @@
 from typing import Annotated
 
-from fastapi_filter import FilterDepends, with_prefix
+from fastapi_filter import with_prefix
 
 from app.db.model import ReconstructionMorphology
+from app.dependencies.filter import FilterDepends
 from app.filters.base import CustomFilter
 from app.filters.common import (
     BrainRegionFilterMixin,
diff --git a/app/filters/person.py b/app/filters/person.py
index 04278d94b..7a82594fa 100644
--- a/app/filters/person.py
+++ b/app/filters/person.py
@@ -1,9 +1,8 @@
 import uuid
 from typing import Annotated
 
-from fastapi_filter import FilterDepends
-
 from app.db.model import Person
+from app.dependencies.filter import FilterDepends
 from app.filters.common import AgentFilter, CreatorFilterMixin
 
 
diff --git a/app/filters/simulation.py b/app/filters/simulation.py
index e9fe2197b..805e6871f 100644
--- a/app/filters/simulation.py
+++ b/app/filters/simulation.py
@@ -1,9 +1,10 @@
 import uuid
 from typing import Annotated
 
-from fastapi_filter import FilterDepends, with_prefix
+from fastapi_filter import with_prefix
 
 from app.db.model import Simulation
+from app.dependencies.filter import FilterDepends
 from app.filters.base import CustomFilter
 from app.filters.common import (
     ContributionFilterMixin,
diff --git a/app/filters/simulation_campaign.py b/app/filters/simulation_campaign.py
index c49298f8a..f8f93f1bc 100644
--- a/app/filters/simulation_campaign.py
+++ b/app/filters/simulation_campaign.py
@@ -1,8 +1,7 @@
 from typing import Annotated
 
-from fastapi_filter import FilterDepends
-
 from app.db.model import SimulationCampaign
+from app.dependencies.filter import FilterDepends
 from app.filters.base import CustomFilter
 from app.filters.common import EntityFilterMixin, NameFilterMixin
 from app.filters.simulation import NestedSimulationFilter, NestedSimulationFilterDep
diff --git a/app/filters/simulation_execution.py b/app/filters/simulation_execution.py
index aacfb39a7..9dc6f19a9 100644
--- a/app/filters/simulation_execution.py
+++ b/app/filters/simulation_execution.py
@@ -1,8 +1,7 @@
 from typing import Annotated
 
-from fastapi_filter import FilterDepends
-
 from app.db.model import SimulationExecution
+from app.dependencies.filter import FilterDepends
 from app.filters.activity import ActivityFilterMixin
 from app.filters.base import CustomFilter
 
diff --git a/app/filters/simulation_generation.py b/app/filters/simulation_generation.py
index 1dddd40ba..bb6d3da72 100644
--- a/app/filters/simulation_generation.py
+++ b/app/filters/simulation_generation.py
@@ -1,8 +1,7 @@
 from typing import Annotated
 
-from fastapi_filter import FilterDepends
-
 from app.db.model import SimulationGeneration
+from app.dependencies.filter import FilterDepends
 from app.filters.activity import ActivityFilterMixin
 from app.filters.base import CustomFilter
 
diff --git a/app/filters/simulation_result.py b/app/filters/simulation_result.py
index d9f478e24..66a1f563c 100644
--- a/app/filters/simulation_result.py
+++ b/app/filters/simulation_result.py
@@ -1,8 +1,9 @@
 from typing import Annotated
 
-from fastapi_filter import FilterDepends, with_prefix
+from fastapi_filter import with_prefix
 
 from app.db.model import SimulationResult
+from app.dependencies.filter import FilterDepends
 from app.filters.base import CustomFilter
 from app.filters.common import (
     ContributionFilterMixin,
diff --git a/app/filters/single_neuron_simulation.py b/app/filters/single_neuron_simulation.py
index e441a3df1..d37ab3e14 100644
--- a/app/filters/single_neuron_simulation.py
+++ b/app/filters/single_neuron_simulation.py
@@ -1,9 +1,8 @@
 from typing import Annotated
 
-from fastapi_filter import FilterDepends
-
 from app.db.model import SingleNeuronSimulation
 from app.db.types import SingleNeuronSimulationStatus
+from app.dependencies.filter import FilterDepends
 from app.filters.base import CustomFilter
 from app.filters.common import (
     BrainRegionFilterMixin,
diff --git a/app/filters/single_neuron_synaptome.py b/app/filters/single_neuron_synaptome.py
index e70c343bc..2335a01a7 100644
--- a/app/filters/single_neuron_synaptome.py
+++ b/app/filters/single_neuron_synaptome.py
@@ -1,8 +1,9 @@
 from typing import Annotated
 
-from fastapi_filter import FilterDepends, with_prefix
+from fastapi_filter import with_prefix
 
 from app.db.model import SingleNeuronSynaptome
+from app.dependencies.filter import FilterDepends
 from app.filters.base import CustomFilter
 from app.filters.common import (
     BrainRegionFilterMixin,
diff --git a/app/filters/single_neuron_synaptome_simulation.py b/app/filters/single_neuron_synaptome_simulation.py
index cf5e66694..a77cde781 100644
--- a/app/filters/single_neuron_synaptome_simulation.py
+++ b/app/filters/single_neuron_synaptome_simulation.py
@@ -1,9 +1,8 @@
 from typing import Annotated
 
-from fastapi_filter import FilterDepends
-
 from app.db.model import SingleNeuronSynaptomeSimulation
 from app.db.types import SingleNeuronSimulationStatus
+from app.dependencies.filter import FilterDepends
 from app.filters.base import CustomFilter
 from app.filters.common import (
     BrainRegionFilterMixin,
diff --git a/app/filters/validation_result.py b/app/filters/validation_result.py
index 632fcd61e..86a5a33e2 100644
--- a/app/filters/validation_result.py
+++ b/app/filters/validation_result.py
@@ -1,9 +1,8 @@
 import uuid
 from typing import Annotated
 
-from fastapi_filter import FilterDepends
-
 from app.db.model import ValidationResult
+from app.dependencies.filter import FilterDepends
 from app.filters.base import CustomFilter
 from app.filters.common import EntityFilterMixin, NameFilterMixin
 
diff --git a/tests/test_circuit.py b/tests/test_circuit.py
index 7279efb96..5ee987ad9 100644
--- a/tests/test_circuit.py
+++ b/tests/test_circuit.py
@@ -181,7 +181,7 @@ def test_filtering(client, root_circuit, models):
         url=ROUTE,
         params={
             "root_circuit_id": str(root_circuit.id),
-            "scale__in": "single,whole_brain",
+            "scale__in": ["single", "whole_brain"],
         },
     ).json()["data"]
     assert len(data) == 4
diff --git a/tests/test_electrical_cell_recording.py b/tests/test_electrical_cell_recording.py
index 8860bf46c..a7c32143c 100644
--- a/tests/test_electrical_cell_recording.py
+++ b/tests/test_electrical_cell_recording.py
@@ -211,7 +211,7 @@ def test_filtering(db, client, electrical_cell_recording_json_data, person_id):
         db,
         [
             Subject(
-                name=f"my-subject-{i}",
+                name=f"subject-{i}",
                 description="my-description",
                 species_id=sp.id,
                 strain_id=None,
@@ -244,7 +244,6 @@ def test_filtering(db, client, electrical_cell_recording_json_data, person_id):
             for i, subject in enumerate(subjects)
         ],
     )
-
     data = assert_request(client.get, url=ROUTE).json()["data"]
     assert len(data) == len(models)
 
@@ -257,3 +256,23 @@ def test_filtering(db, client, electrical_cell_recording_json_data, person_id):
         "data"
     ]
     assert len(data) == 2
+
+    data = assert_request(client.get, url=ROUTE, params="subject__species__name=species-2").json()[
+        "data"
+    ]
+    assert len(data) == 2
+
+    data = assert_request(
+        client.get,
+        url=ROUTE,
+        params={"name__in": ["e-1", "e-2"]},
+    ).json()["data"]
+    assert {d["name"] for d in data} == {"e-1", "e-2"}
+
+    # backwards compat
+    data = assert_request(
+        client.get,
+        url=ROUTE,
+        params={"name__in": "e-1,e-2"},
+    ).json()["data"]
+    assert {d["name"] for d in data} == {"e-1", "e-2"}
diff --git a/tests/test_etype.py b/tests/test_etype.py
index 0848e27ab..7801c57a4 100644
--- a/tests/test_etype.py
+++ b/tests/test_etype.py
@@ -45,12 +45,20 @@ def test_retrieve(db, client, person_id):
     assert data[0] == with_creation_fields(items[5])
 
     # test filter (in)
+
+    # backwards compat
     response = client.get(ROUTE, params={"pref_label__in": "pref_label_5,pref_label_6"})
     assert response.status_code == 200
     data = response.json()["data"]
     assert len(data) == 2
     assert data == [with_creation_fields(items[5]), with_creation_fields(items[6])]
 
+    response = client.get(ROUTE, params={"pref_label__in": ["pref_label_5", "pref_label_6"]})
+    assert response.status_code == 200
+    data = response.json()["data"]
+    assert len(data) == 2
+    assert data == [with_creation_fields(items[5]), with_creation_fields(items[6])]
+
     response = client.get(f"{ROUTE}/{etypes[0].id}")
     assert response.status_code == 200
     data = response.json()
diff --git a/tests/test_morphology.py b/tests/test_morphology.py
index b96e5d5d7..48f84752a 100644
--- a/tests/test_morphology.py
+++ b/tests/test_morphology.py
@@ -582,6 +582,8 @@ def test_filter_by_id__in(db, client, brain_region_id, person_id):
 
     # filtering by multiple IDs
     selected_ids = [morphology_ids[1], morphology_ids[3]]
+
+    # backwards compat
     response = client.get(ROUTE, params={"id__in": ",".join(selected_ids)})
     assert response.status_code == 200
     data = response.json()["data"]
@@ -589,7 +591,16 @@ def test_filter_by_id__in(db, client, brain_region_id, person_id):
     returned_ids = [item["id"] for item in data]
     assert set(returned_ids) == set(selected_ids)
 
+    response = client.get(ROUTE, params={"id__in": selected_ids})
+    assert response.status_code == 200
+    data = response.json()["data"]
+    assert len(data) == 2
+    returned_ids = [item["id"] for item in data]
+    assert set(returned_ids) == set(selected_ids)
+
     # filtering by all IDs
+
+    # backwards compat
     response = client.get(ROUTE, params={"id__in": ",".join(morphology_ids)})
     assert response.status_code == 200
     data = response.json()["data"]
@@ -597,6 +608,13 @@ def test_filter_by_id__in(db, client, brain_region_id, person_id):
     returned_ids = [item["id"] for item in data]
     assert set(returned_ids) == set(morphology_ids)
 
+    response = client.get(ROUTE, params={"id__in": morphology_ids})
+    assert response.status_code == 200
+    data = response.json()["data"]
+    assert len(data) == 5
+    returned_ids = [item["id"] for item in data]
+    assert set(returned_ids) == set(morphology_ids)
+
     # filtering by non-existent ID
     response = client.get(ROUTE, params={"id__in": MISSING_ID})
     assert response.status_code == 200
@@ -604,6 +622,8 @@ def test_filter_by_id__in(db, client, brain_region_id, person_id):
     assert len(data) == 0
 
     # combining id__in with other filters
+
+    # backwards compat
     response = client.get(
         ROUTE,
         params={"id__in": ",".join(morphology_ids), "name__ilike": "%Filter Test Morphology 2%"},
@@ -613,6 +633,15 @@ def test_filter_by_id__in(db, client, brain_region_id, person_id):
     assert len(data) == 1
     assert data[0]["id"] == morphology_ids[2]
 
+    response = client.get(
+        ROUTE,
+        params={"id__in": morphology_ids, "name__ilike": "%Filter Test Morphology 2%"},
+    )
+    assert response.status_code == 200
+    data = response.json()["data"]
+    assert len(data) == 1
+    assert data[0]["id"] == morphology_ids[2]
+
 
 def test_brain_region_filter(db, client, brain_region_hierarchy_id, species_id, person_id):
     def create_model_function(_db, name, brain_region_id):
diff --git a/tests/test_mtype.py b/tests/test_mtype.py
index 01d3f8a1b..180262089 100644
--- a/tests/test_mtype.py
+++ b/tests/test_mtype.py
@@ -46,12 +46,19 @@ def test_retrieve(db, client, person_id):
     assert data[0] == with_creation_fields(items[5])
 
     # test filter (in)
+    # backwards compat
     response = client.get(ROUTE, params={"pref_label__in": "pref_label_5,pref_label_6"})
     assert response.status_code == 200
     data = response.json()["data"]
     assert len(data) == 2
     assert data == [with_creation_fields(items[5]), with_creation_fields(items[6])]
 
+    response = client.get(ROUTE, params={"pref_label__in": ["pref_label_5", "pref_label_6"]})
+    assert response.status_code == 200
+    data = response.json()["data"]
+    assert len(data) == 2
+    assert data == [with_creation_fields(items[5]), with_creation_fields(items[6])]
+
     response = client.get(f"{ROUTE}/{mtypes[0].id}")
     assert response.status_code == 200
     data = response.json()
diff --git a/tests/test_simulation_execution.py b/tests/test_simulation_execution.py
index 174bb03d7..c73896c87 100644
--- a/tests/test_simulation_execution.py
+++ b/tests/test_simulation_execution.py
@@ -247,11 +247,20 @@ def test_filtering(client, models, root_circuit, simulation_result):
     ).json()["data"]
     assert len(data) == 2
 
+    # backwards compat
     data = assert_request(
         client.get, url=ROUTE, params={"used__id__in": f"{root_circuit.id},{simulation_result.id}"}
     ).json()["data"]
     assert len(data) == 5
 
+    data = assert_request(
+        client.get,
+        url=ROUTE,
+        params={"used__id__in": [str(root_circuit.id), str(simulation_result.id)]},
+    ).json()["data"]
+    assert len(data) == 5
+
+    # backwards compat
     data = assert_request(
         client.get,
         url=ROUTE,
@@ -259,6 +268,13 @@ def test_filtering(client, models, root_circuit, simulation_result):
     ).json()["data"]
     assert len(data) == 4
 
+    data = assert_request(
+        client.get,
+        url=ROUTE,
+        params={"generated__id__in": [str(root_circuit.id), str(simulation_result.id)]},
+    ).json()["data"]
+    assert len(data) == 4
+
 
 def test_delete_one(db, client, models):
     # sanity check
diff --git a/tests/test_simulation_generation.py b/tests/test_simulation_generation.py
index f0a40ef66..5fe8bcd81 100644
--- a/tests/test_simulation_generation.py
+++ b/tests/test_simulation_generation.py
@@ -226,11 +226,20 @@ def test_filtering(client, models, root_circuit, simulation_result):
     ).json()["data"]
     assert len(data) == 2
 
+    # backwards compat
     data = assert_request(
         client.get, url=ROUTE, params={"used__id__in": f"{root_circuit.id},{simulation_result.id}"}
     ).json()["data"]
     assert len(data) == 5
 
+    data = assert_request(
+        client.get,
+        url=ROUTE,
+        params={"used__id__in": [str(root_circuit.id), str(simulation_result.id)]},
+    ).json()["data"]
+    assert len(data) == 5
+
+    # backwards compat
     data = assert_request(
         client.get,
         url=ROUTE,
@@ -238,6 +247,13 @@ def test_filtering(client, models, root_circuit, simulation_result):
     ).json()["data"]
     assert len(data) == 4
 
+    data = assert_request(
+        client.get,
+        url=ROUTE,
+        params={"generated__id__in": [str(root_circuit.id), str(simulation_result.id)]},
+    ).json()["data"]
+    assert len(data) == 4
+
 
 def test_delete_one(db, client, models):
     # sanity check