diff --git a/src/timeseriesflattener/v1/feature_specs/group_specs.py b/src/timeseriesflattener/v1/feature_specs/group_specs.py
index 21822e00..e9ec383c 100644
--- a/src/timeseriesflattener/v1/feature_specs/group_specs.py
+++ b/src/timeseriesflattener/v1/feature_specs/group_specs.py
@@ -106,7 +106,7 @@ def create_combinations(self) -> List[OutcomeSpec]:
         ]
 
 
-GroupSpec = PredictorGroupSpec | OutcomeGroupSpec
+GroupSpec = Union[PredictorGroupSpec, OutcomeGroupSpec]
 
 
 def create_feature_combinations_from_dict(
diff --git a/src/timeseriesflattener/v1/feature_specs/single_specs.py b/src/timeseriesflattener/v1/feature_specs/single_specs.py
index 399a2ca4..bb1a8b2e 100644
--- a/src/timeseriesflattener/v1/feature_specs/single_specs.py
+++ b/src/timeseriesflattener/v1/feature_specs/single_specs.py
@@ -192,5 +192,5 @@ def get_output_col_name(self) -> str:
         )
 
 
-TemporalSpec = PredictorSpec | OutcomeSpec
-AnySpec = StaticSpec | TemporalSpec
+TemporalSpec = Union[PredictorSpec, OutcomeSpec]
+AnySpec = Union[StaticSpec, TemporalSpec]