diff --git a/moto/s3/models.py b/moto/s3/models.py
index 0a84ba731..69ef827ff 100644
--- a/moto/s3/models.py
+++ b/moto/s3/models.py
@@ -104,17 +104,18 @@ class S3Backend(BaseBackend):
         if prefix:
             for key_name, key in bucket.keys.iteritems():
                 if key_name.startswith(prefix):
-                    if delimiter and '/' in key_name.lstrip(prefix):
+                    key_without_prefix = key_name.replace(prefix, "", 1)
+                    if delimiter and delimiter in key_without_prefix:
                         # If delimiter, we need to split out folder_results
-                        key_without_prefix = "{}/".format(key_name.lstrip(prefix).split("/")[0])
-                        folder_results.add("{}{}".format(prefix, key_without_prefix))
+                        key_without_delimiter = key_without_prefix.split(delimiter)[0]
+                        folder_results.add("{}{}{}".format(prefix, key_without_delimiter, delimiter))
                     else:
                         key_results.add(key)
         else:
             for key_name, key in bucket.keys.iteritems():
-                if delimiter and '/' in key_name:
+                if delimiter and delimiter in key_name:
                     # If delimiter, we need to split out folder_results
-                    folder_results.add(key_name.split("/")[0])
+                    folder_results.add(key_name.split(delimiter)[0])
                 else:
                     key_results.add(key)
 
diff --git a/moto/s3/responses.py b/moto/s3/responses.py
index 1d69384da..766c06e9f 100644
--- a/moto/s3/responses.py
+++ b/moto/s3/responses.py
@@ -37,7 +37,7 @@ def _bucket_response(request, full_url, headers):
         bucket = s3_backend.get_bucket(bucket_name)
         if bucket:
             prefix = querystring.get('prefix', [None])[0]
-            delimiter = querystring.get('delimiter')
+            delimiter = querystring.get('delimiter', [None])[0]
             result_keys, result_folders = s3_backend.prefix_query(bucket, prefix, delimiter)
             template = Template(S3_BUCKET_GET_RESPONSE)
             return template.render(
diff --git a/tests/test_s3/test_s3.py b/tests/test_s3/test_s3.py
index 264b8bb08..54da1b9ac 100644
--- a/tests/test_s3/test_s3.py
+++ b/tests/test_s3/test_s3.py
@@ -227,3 +227,11 @@ def test_bucket_key_listing_order():
     delimiter = '/'
     keys = [x.name for x in bucket.list(prefix=None, delimiter=delimiter)]
     keys.should.equal(['toplevel'])
+
+    delimiter = None
+    keys = [x.name for x in bucket.list(prefix + 'x', delimiter)]
+    keys.should.equal([u'toplevel/x/key', u'toplevel/x/y/key', u'toplevel/x/y/z/key'])
+
+    delimiter = '/'
+    keys = [x.name for x in bucket.list(prefix + 'x', delimiter)]
+    keys.should.equal([u'toplevel/x/'])