diff --git a/swift/obj/mem_diskfile.py b/swift/obj/mem_diskfile.py
index e86c321e2f..a3b37f4834 100644
--- a/swift/obj/mem_diskfile.py
+++ b/swift/obj/mem_diskfile.py
@@ -43,17 +43,37 @@ class InMemoryFileSystem(object):
         self._filesystem = {}
 
     def get_object(self, name):
+        """
+        Return back an file-like object and its metadata
+
+        :param name: standard object name
+        :return (fp, metadata): fp is `StringIO` in-memory representation
+                                object (or None). metadata is a dictionary
+                                of metadata (or None)
+        """
         val = self._filesystem.get(name)
         if val is None:
-            data, metadata = None, None
+            fp, metadata = None, None
         else:
-            data, metadata = val
-        return data, metadata
+            fp, metadata = val
+        return fp, metadata
 
-    def put_object(self, name, data, metadata):
-        self._filesystem[name] = (data, metadata)
+    def put_object(self, name, fp, metadata):
+        """
+        Store object into memory
+
+        :param name: standard object name
+        :param fp: `StringIO` in-memory representation object
+        :param metadata: dictionary of metadata to be written
+        """
+        self._filesystem[name] = (fp, metadata)
 
     def del_object(self, name):
+        """
+        Delete object from memory
+
+        :param name: standard object name
+        """
         del self._filesystem[name]
 
     def get_diskfile(self, account, container, obj, **kwargs):
diff --git a/test/unit/proxy/test_server.py b/test/unit/proxy/test_server.py
index 551b51af22..5f9d03094d 100644
--- a/test/unit/proxy/test_server.py
+++ b/test/unit/proxy/test_server.py
@@ -2970,6 +2970,10 @@ class TestObjectController(unittest.TestCase):
 
         # now POST to the object using default object_post_as_copy setting
         orig_post_as_copy = prosrv.object_post_as_copy
+
+        # last-modified rounded in sec so sleep a sec to increment
+        sleep(1)
+
         sock = connect_tcp(('localhost', prolis.getsockname()[1]))
         fd = sock.makefile()
         fd.write('POST /v1/a/c/o.last_modified HTTP/1.1\r\n'
@@ -2984,10 +2988,14 @@ class TestObjectController(unittest.TestCase):
 
         # last modified time will have changed due to POST
         last_modified_head = _do_HEAD()
+        self.assertNotEqual(last_modified_put, last_modified_head)
         _do_conditional_GET_checks(last_modified_head)
 
         # now POST using non-default object_post_as_copy setting
         try:
+            # last-modified rounded in sec so sleep a sec to increment
+            last_modified_post = last_modified_head
+            sleep(1)
             prosrv.object_post_as_copy = not orig_post_as_copy
             sock = connect_tcp(('localhost', prolis.getsockname()[1]))
             fd = sock.makefile()
@@ -3005,6 +3013,7 @@ class TestObjectController(unittest.TestCase):
 
         # last modified time will have changed due to POST
         last_modified_head = _do_HEAD()
+        self.assertNotEqual(last_modified_post, last_modified_head)
         _do_conditional_GET_checks(last_modified_head)
 
     def test_PUT_auto_content_type(self):