diff --git a/nomad/normalizing/results.py b/nomad/normalizing/results.py
index b7cf5e6b213bd23a31c983fe4801a3e9c3c8d446..42fd4b482ee89715d6f31b3e8aba5becc4c83c22 100644
--- a/nomad/normalizing/results.py
+++ b/nomad/normalizing/results.py
@@ -1074,7 +1074,9 @@ class ResultsNormalizer(Normalizer):
                             )
                             msd.diffusion_constant_errors = (
                                 diffusion_constant.errors
-                                if isinstance(diffusion_constant.errors, list)
+                                if isinstance(
+                                    diffusion_constant.errors, (list, np.ndarray)
+                                )
                                 else [diffusion_constant.errors]
                             )