diff --git a/src/finn/custom_op/fpgadataflow/labelselect_batch.py b/src/finn/custom_op/fpgadataflow/labelselect_batch.py
index 264ab51fdbab08959d05998e8f70c70e1ebed8af..7591f09d8d0cd1847672fe5aa09616ff1571033d 100644
--- a/src/finn/custom_op/fpgadataflow/labelselect_batch.py
+++ b/src/finn/custom_op/fpgadataflow/labelselect_batch.py
@@ -149,7 +149,9 @@ class LabelSelect_Batch(HLSCustomOp):
 
     def get_input_datatype(self):
         """Returns FINN DataType of input."""
-        return DataType[self.get_nodeattr("inputDataType")]
+        ret = DataType[self.get_nodeattr("inputDataType")]
+        assert ret.signed() is False, "LabelSelect is currently broken for signed inputs"
+        return ret
 
     def get_output_datatype(self):
         """Returns FINN DataType of output."""