diff --git a/rasa_sdk/tracing/instrumentation/attribute_extractors.py b/rasa_sdk/tracing/instrumentation/attribute_extractors.py
index 74804d600..80183ac3a 100644
--- a/rasa_sdk/tracing/instrumentation/attribute_extractors.py
+++ b/rasa_sdk/tracing/instrumentation/attribute_extractors.py
@@ -1,3 +1,5 @@
+import json
+
 from typing import Any, Dict, Text
 from rasa_sdk.executor import ActionExecutor, CollectingDispatcher
 from rasa_sdk.forms import ValidationAction
@@ -51,6 +53,6 @@ def extract_attrs_for_validation_action(
     return {
         "class_name": self.__class__.__name__,
         "sender_id": tracker.sender_id,
-        "slots_to_validate": str(slots_to_validate),
+        "slots_to_validate": json.dumps(list(slots_to_validate)),
         "action_name": self.name(),
     }
diff --git a/tests/tracing/instrumentation/test_validation_action.py b/tests/tracing/instrumentation/test_validation_action.py
index f8ffebdeb..5f745dd06 100644
--- a/tests/tracing/instrumentation/test_validation_action.py
+++ b/tests/tracing/instrumentation/test_validation_action.py
@@ -17,10 +17,10 @@
 @pytest.mark.parametrize(
     "events, expected_slots_to_validate",
     [
-        ([], "dict_keys([])"),
+        ([], "[]"),
         (
             [SlotSet("name", "Tom"), SlotSet("address", "Berlin")],
-            "dict_keys(['name', 'address'])",
+            '["name", "address"]',
         ),
     ],
 )