diff --git a/bilby/gw/conversion.py b/bilby/gw/conversion.py
index 24ae47ba406f2d46e10d7c781c1dcc1f5083f45f..8b5b4ecbc778c22096ee2ce3e6599aa6d9684a33 100644
--- a/bilby/gw/conversion.py
+++ b/bilby/gw/conversion.py
@@ -1566,4 +1566,4 @@ def fill_sample(args):
     sample = dict(sample).copy()
     likelihood.parameters.update(dict(sample).copy())
     new_sample = likelihood.generate_posterior_sample_from_marginalized_likelihood()
-    return (new_sample[key] for key in marginalized_parameters)
+    return tuple((new_sample[key] for key in marginalized_parameters))