diff --git a/moto/core/responses.py b/moto/core/responses.py
index da3eefe74..b63186288 100644
--- a/moto/core/responses.py
+++ b/moto/core/responses.py
@@ -916,6 +916,8 @@ def to_str(value, spec):
     vtype = spec["type"]
     if vtype == "boolean":
         return "true" if value else "false"
+    elif vtype == "long":
+        return int(value)
     elif vtype == "integer":
         return str(value)
     elif vtype == "float":
diff --git a/tests/test_emr/test_emr_boto3.py b/tests/test_emr/test_emr_boto3.py
index 5e1014ef1..06f14b08e 100644
--- a/tests/test_emr/test_emr_boto3.py
+++ b/tests/test_emr/test_emr_boto3.py
@@ -117,6 +117,7 @@ def test_describe_cluster():
     args["Tags"] = [{"Key": "tag1", "Value": "val1"}, {"Key": "tag2", "Value": "val2"}]
     args["SecurityConfiguration"] = "my-security-configuration"
     args["AutoScalingRole"] = "EMR_AutoScaling_DefaultRole"
+    args["AutoTerminationPolicy"] = {"IdleTimeout": 123}
 
     cluster_id = client.run_job_flow(**args)["JobFlowId"]