diff --git a/swift/common/utils.py b/swift/common/utils.py
index febeeaab72..4540858f8e 100644
--- a/swift/common/utils.py
+++ b/swift/common/utils.py
@@ -425,7 +425,11 @@ def drop_buffer_cache(fd, offset, length):
 def normalize_timestamp(timestamp):
     """
     Format a timestamp (string or numeric) into a standardized
-    xxxxxxxxxx.xxxxx format.
+    xxxxxxxxxx.xxxxx (10.5) format.
+
+    Note that timestamps using values greater than or equal to November 20th,
+    2286 at 17:46 UTC will use 11 digits to represent the number of
+    seconds.
 
     :param timestamp: unix timestamp
     :returns: normalized timestamp as a string
diff --git a/swift/proxy/controllers/obj.py b/swift/proxy/controllers/obj.py
index 6609eb9884..c2171f73c7 100644
--- a/swift/proxy/controllers/obj.py
+++ b/swift/proxy/controllers/obj.py
@@ -861,7 +861,7 @@ class ObjectController(Controller):
         if 'x-timestamp' in req.headers:
             try:
                 req.headers['X-Timestamp'] = \
-                    normalize_timestamp(float(req.headers['x-timestamp']))
+                    normalize_timestamp(req.headers['x-timestamp'])
                 if hresp.environ and 'swift_x_timestamp' in hresp.environ and \
                     float(hresp.environ['swift_x_timestamp']) >= \
                         float(req.headers['x-timestamp']):
@@ -1210,7 +1210,7 @@ class ObjectController(Controller):
         if 'x-timestamp' in req.headers:
             try:
                 req.headers['X-Timestamp'] = \
-                    normalize_timestamp(float(req.headers['x-timestamp']))
+                    normalize_timestamp(req.headers['x-timestamp'])
             except ValueError:
                 return HTTPBadRequest(
                     request=req, content_type='text/plain',