diff --git a/servicex_analysis_utils/file_peeking.py b/servicex_analysis_utils/file_peeking.py
index 9a020b3..a57dce9 100644
--- a/servicex_analysis_utils/file_peeking.py
+++ b/servicex_analysis_utils/file_peeking.py
@@ -32,6 +32,7 @@
 import awkward as ak
 import json
 import logging
+from servicex.dataset_identifier import DataSetIdentifier
 
 
 def run_query(input_filenames):
@@ -85,8 +86,8 @@ def build_deliver_spec(datasets):
     Supports multiple inputs for multiple sample queries.
 
     Parameters:
-    datasets (str, [str], or dict): Rucio DIDs to be checked by the servicex workers.
-                                   If dict, custom names can be inputed
+    datasets (str, [str], dict, DataSetIdentifier): Rucio DIDs (str) or DataSetIdentifier object.
+                                                    If dict, custom names can be inputed for each dataset
 
     Returns:
     spec_python (dict): The specification for the python function query containing Name, Query, Dataset, NFiles
@@ -98,23 +99,29 @@ def build_deliver_spec(datasets):
     dataset_dict = {}
     user_in = type(datasets)
 
+    # Rucio DID as str
     if user_in == str:
-        dataset_dict.update({datasets: datasets})
+        dataset_dict.update({datasets: datasets})  # Use dataset ID as sample name
     elif user_in == list and type(datasets[0]) is str:
         for ds in datasets:
             dataset_dict.update({ds: ds})
-    elif user_in == dict:
+    elif user_in == dict:  # Custom sample names
         dataset_dict = datasets
+    # Single DataSetIdentifier object
+    elif isinstance(datasets, DataSetIdentifier):
+        dataset_dict.update({"Dataset": datasets})
     else:
         raise ValueError(
-            f"Unsupported dataset input type: {user_in}.\nInput must be dict ('sample_name':'dataset_id'), str or list of str"
+            f"Unsupported dataset input type: {user_in}.\n"
+            "Input must be str or list of str of Rucio DIDs, "
+            "a DataSetIdentifier object or a dict ('sample_name':'dataset_id')"
         )
 
     sample_list = [
         {
             "NFiles": 1,
             "Name": name,
-            "Dataset": dataset.Rucio(did),
+            "Dataset": dataset.Rucio(did) if isinstance(did, str) else did,
             "Query": query_PythonFunction,
         }
         for name, did in dataset_dict.items()
diff --git a/tests/test_file_peeking.py b/tests/test_file_peeking.py
index 4e32e23..b2a8cd2 100644
--- a/tests/test_file_peeking.py
+++ b/tests/test_file_peeking.py
@@ -34,6 +34,14 @@
 import re
 import filecmp
 from servicex_analysis_utils import file_peeking
+from servicex import dataset
+from servicex.python_dataset import PythonFunction
+from servicex.dataset_identifier import (
+    RucioDatasetIdentifier,
+    FileListDataset,
+    CERNOpenDataDatasetIdentifier,
+    XRootDDatasetIdentifier,
+)
 
 
 @pytest.fixture
@@ -146,14 +154,10 @@ def test_spec_builder():
     assert isinstance(first_entry["NFiles"], int), "'NFiles' should be an integer"
     assert isinstance(first_entry["Name"], str), "'Name' should be a string"
 
-    from servicex.dataset_identifier import RucioDatasetIdentifier
-
     assert isinstance(
         first_entry["Dataset"], RucioDatasetIdentifier
     ), "'Dataset' should be a RucioDatasetIdentifier"
 
-    from servicex.python_dataset import PythonFunction
-
     assert isinstance(
         first_entry["Query"], PythonFunction
     ), "'Query' should be a PythonFunction"
@@ -173,15 +177,65 @@ def test_spec_builder():
 
     # wrong input type
     wrong_did = 1234
+    expected_msg = (
+        f"Unsupported dataset input type: {type(wrong_did)}.\n"
+        "Input must be str or list of str of Rucio DIDs, "
+        "a DataSetIdentifier object or a dict "
+        "('sample_name':'dataset_id')"
+    )
+
     with pytest.raises(
         ValueError,
-        match=re.escape(
-            f"Unsupported dataset input type: {type(wrong_did)}.\nInput must be dict ('sample_name':'dataset_id'), str or list of str"
-        ),
+        match=re.escape(expected_msg),
     ):
         file_peeking.build_deliver_spec(wrong_did)
 
 
+def test_spec_builder_with_dataset_identifier():
+    # Build multiple types of dataset identifiers
+    ds1 = dataset.Rucio("random_space:did")
+    ds2 = dataset.XRootD("root://server/file.root")
+    ds3 = dataset.CERNOpenData("cernopendata:12345")
+    ds4 = dataset.FileList(["file1.root", "file2.root"])
+
+    ds_list = [ds1, ds2, ds3, ds4]
+    ds_types = [
+        RucioDatasetIdentifier,
+        XRootDDatasetIdentifier,
+        CERNOpenDataDatasetIdentifier,
+        FileListDataset,
+    ]
+    for did, did_type in zip(ds_list, ds_types):
+        spec = file_peeking.build_deliver_spec(did)
+
+        # Check return type
+        assert isinstance(spec, dict), "build_deliver_spec does not return a dict"
+        assert "Sample" in spec, "Key 'Sample' is missing in the returned dict"
+        assert isinstance(spec["Sample"], list), "'Sample' should be a list"
+
+        # Get return size
+        size = len(spec["Sample"])
+        assert (
+            size == 1
+        ), f"Only one did given but sample item of spec is not len 1: {size}"
+
+        # Check first sample
+        first_entry = spec["Sample"][0]
+        assert isinstance(first_entry, dict), "Each entry in 'Sample' should be a dict"
+
+        # Check each key type
+        assert isinstance(first_entry["NFiles"], int), "'NFiles' should be an integer"
+        assert isinstance(first_entry["Name"], str), "'Name' should be a string"
+
+        assert isinstance(
+            first_entry["Query"], PythonFunction
+        ), "'Query' should be a PythonFunction"
+
+        assert isinstance(
+            first_entry["Dataset"], did_type
+        ), f"Input Dataset identifier {did} should be a {did_type} but is {type(first_entry['Dataset'])}"
+
+
 def test_decoding_to_array(build_test_samples, array_out=True):
     path = build_test_samples
     query_output = file_peeking.run_query(path)