diff --git a/superset/dataframe.py b/superset/dataframe.py
index 47683b0cc0d4..c1733362d807 100644
--- a/superset/dataframe.py
+++ b/superset/dataframe.py
@@ -110,7 +110,7 @@ def __init__(self, data, cursor_description, db_engine_spec):
             # need to do this because we can not specify a mixed dtype when
             # instantiating the DataFrame, and this allows us to have different
             # dtypes for each column.
-            array = np.array(data)
+            array = np.array(data, dtype="object")
             data = {
                 column: pd.Series(array[:, i], dtype=dtype[column])
                 for i, column in enumerate(column_names)