diff --git a/datadog_lambda/trigger.py b/datadog_lambda/trigger.py
index 0cd7f56b..6958b9de 100644
--- a/datadog_lambda/trigger.py
+++ b/datadog_lambda/trigger.py
@@ -461,6 +461,8 @@ def is_step_function_event(event):
     The actual event must contain "Execution", "StateMachine", and "State" fields.
     """
     event = event.get("Payload", event)
+    if not isinstance(event, dict):
+        return False
 
     # JSONPath style
     if "Execution" in event and "StateMachine" in event and "State" in event:
diff --git a/tests/test_trigger.py b/tests/test_trigger.py
index 477aeec1..eb21f1e3 100644
--- a/tests/test_trigger.py
+++ b/tests/test_trigger.py
@@ -757,3 +757,7 @@ def test_is_step_function_event_dd_header(self):
             }
         }
         self.assertFalse(is_step_function_event(event))
+
+    def test_is_step_function_event_payload_not_dict(self):
+        event = {"Payload": "This is a string, not a dict"}
+        self.assertFalse(is_step_function_event(event))