diff --git a/src/pysdmx/fmr/fusion/dsd.py b/src/pysdmx/fmr/fusion/dsd.py
index 9ae1747..4e30b36 100644
--- a/src/pysdmx/fmr/fusion/dsd.py
+++ b/src/pysdmx/fmr/fusion/dsd.py
@@ -40,7 +40,7 @@ def _get_representation(
     cls: Sequence[FusionCodelist],
     cons: Dict[str, Sequence[str]],
 ) -> Tuple[
-    DataType,
+    Optional[DataType],
     Optional[Facets],
     Optional[Codelist],
     Optional[ArrayBoundaries],
diff --git a/src/pysdmx/fmr/sdmx/dsd.py b/src/pysdmx/fmr/sdmx/dsd.py
index 5669ce7..b9eec7d 100644
--- a/src/pysdmx/fmr/sdmx/dsd.py
+++ b/src/pysdmx/fmr/sdmx/dsd.py
@@ -45,7 +45,7 @@ def _get_representation(
     cls: Sequence[Codelist],
     cons: Dict[str, Sequence[str]],
 ) -> Tuple[
-    DataType,
+    Optional[DataType],
     Optional[Facets],
     Optional[Codelist],
     Optional[ArrayBoundaries],