diff --git a/superset/result_set.py b/superset/result_set.py
index b8a5abb6d192..cf57ddc84af5 100644
--- a/superset/result_set.py
+++ b/superset/result_set.py
@@ -63,8 +63,13 @@ def stringify(obj: Any) -> str:
 
 
 def stringify_values(array: np.ndarray) -> np.ndarray:
-    vstringify = np.vectorize(stringify)
-    return vstringify(array)
+    result = np.copy(array)
+
+    with np.nditer(result, flags=["refs_ok"], op_flags=["readwrite"]) as it:
+        for obj in it:
+            obj[...] = stringify(obj)
+
+    return result
 
 
 def destringify(obj: str) -> Any: