diff --git a/moto/s3/responses.py b/moto/s3/responses.py
index a7fb82210..e4259b57f 100644
--- a/moto/s3/responses.py
+++ b/moto/s3/responses.py
@@ -1774,7 +1774,9 @@ S3_BUCKET_GET_RESPONSE = """<?xml version="1.0" encoding="UTF-8"?>
   <Prefix>{{ prefix }}</Prefix>
   {% endif %}
   <MaxKeys>{{ max_keys }}</MaxKeys>
-  <Delimiter>{{ delimiter }}</Delimiter>
+  {% if delimiter %}
+    <Delimiter>{{ delimiter }}</Delimiter>
+  {% endif %}
   <IsTruncated>{{ is_truncated }}</IsTruncated>
   {% if next_marker %}
     <NextMarker>{{ next_marker }}</NextMarker>
diff --git a/tests/test_s3/test_s3.py b/tests/test_s3/test_s3.py
index 8cc9a740c..b213a9a72 100644
--- a/tests/test_s3/test_s3.py
+++ b/tests/test_s3/test_s3.py
@@ -1709,6 +1709,17 @@ def test_website_redirect_location():
     resp["WebsiteRedirectLocation"].should.equal(url)
 
 
+@mock_s3
+def test_delimiter_optional_in_response():
+    s3 = boto3.client("s3", region_name=DEFAULT_REGION_NAME)
+    s3.create_bucket(Bucket="mybucket")
+    s3.put_object(Bucket="mybucket", Key="one", Body=b"1")
+    resp = s3.list_objects(Bucket="mybucket", MaxKeys=1)
+    assert resp.get("Delimiter") is None
+    resp = s3.list_objects(Bucket="mybucket", MaxKeys=1, Delimiter="/")
+    assert resp.get("Delimiter") == "/"
+
+
 @mock_s3
 def test_boto3_list_objects_truncated_response():
     s3 = boto3.client("s3", region_name=DEFAULT_REGION_NAME)
@@ -1725,7 +1736,7 @@ def test_boto3_list_objects_truncated_response():
     assert resp["MaxKeys"] == 1
     assert resp["IsTruncated"] == True
     assert resp.get("Prefix") is None
-    assert resp["Delimiter"] == "None"
+    assert resp.get("Delimiter") is None
     assert "NextMarker" in resp
 
     next_marker = resp["NextMarker"]
@@ -1738,7 +1749,7 @@ def test_boto3_list_objects_truncated_response():
     assert resp["MaxKeys"] == 1
     assert resp["IsTruncated"] == True
     assert resp.get("Prefix") is None
-    assert resp["Delimiter"] == "None"
+    assert resp.get("Delimiter") is None
     assert "NextMarker" in resp
 
     next_marker = resp["NextMarker"]
@@ -1751,7 +1762,7 @@ def test_boto3_list_objects_truncated_response():
     assert resp["MaxKeys"] == 1
     assert resp["IsTruncated"] == False
     assert resp.get("Prefix") is None
-    assert resp["Delimiter"] == "None"
+    assert resp.get("Delimiter") is None
     assert "NextMarker" not in resp