diff --git a/optimas/utils/other.py b/optimas/utils/other.py
index 29e56206..103993fc 100644
--- a/optimas/utils/other.py
+++ b/optimas/utils/other.py
@@ -48,7 +48,10 @@ def convert_to_dataframe(
     # Get fields in given data.
     if isinstance(data, np.ndarray):
         # Labels with multidimensional arrays are converted to a list of lists.
-        d = {label: data[label].tolist() for label in data.dtype.names}
+        d = {
+            label: data[label].tolist() if data[label].ndim > 1 else data[label]
+            for label in data.dtype.names
+        }
         return pd.DataFrame(d)
     elif isinstance(data, pd.DataFrame):
         return data