diff --git a/gnocchi/carbonara.py b/gnocchi/carbonara.py
index 26dac750f..81fbc826d 100644
--- a/gnocchi/carbonara.py
+++ b/gnocchi/carbonara.py
@@ -65,9 +65,15 @@ class SerializableMixin(object):
 
 
 class TimeSerie(SerializableMixin):
+    """A representation of series of a timestamp with a value.
+
+    Duplicate timestamps are not allowed and will be filtered to use the
+    last in the group when the TimeSerie is created or extended.
+    """
 
     def __init__(self, timestamps=None, values=None):
-        self.ts = pandas.Series(values, timestamps).sort_index()
+        self.ts = pandas.Series(values, timestamps).groupby(
+            level=0).last().sort_index()
 
     def __eq__(self, other):
         return (isinstance(other, TimeSerie)
@@ -77,7 +83,8 @@ class TimeSerie(SerializableMixin):
         return self.ts[key]
 
     def set_values(self, values):
-        t = pandas.Series(*reversed(list(zip(*values))))
+        t = pandas.Series(*reversed(list(zip(*values)))).groupby(
+            level=0).last()
         self.ts = t.combine_first(self.ts).sort_index()
 
     def __len__(self):
diff --git a/gnocchi/tests/test_carbonara.py b/gnocchi/tests/test_carbonara.py
index a611bdcf0..8b83e86b0 100644
--- a/gnocchi/tests/test_carbonara.py
+++ b/gnocchi/tests/test_carbonara.py
@@ -74,6 +74,27 @@ class TestBoundTimeSerie(base.BaseTestCase):
                        (datetime.datetime(2014, 1, 1, 12, 0, 10), 4)])
         self.assertEqual(2, len(ts))
 
+    def test_duplicate_timestamps(self):
+        ts = carbonara.BoundTimeSerie(
+            [datetime.datetime(2014, 1, 1, 12, 0, 0),
+             datetime.datetime(2014, 1, 1, 12, 0, 9),
+             datetime.datetime(2014, 1, 1, 12, 0, 9)],
+            [10, 5, 23])
+        self.assertEqual(2, len(ts))
+        self.assertEqual(10.0, ts[0])
+        self.assertEqual(23.0, ts[1])
+
+        ts.set_values([(datetime.datetime(2014, 1, 1, 13, 0, 10), 3),
+                       (datetime.datetime(2014, 1, 1, 13, 0, 11), 9),
+                       (datetime.datetime(2014, 1, 1, 13, 0, 11), 8),
+                       (datetime.datetime(2014, 1, 1, 13, 0, 11), 7),
+                       (datetime.datetime(2014, 1, 1, 13, 0, 11), 4)])
+        self.assertEqual(4, len(ts))
+        self.assertEqual(10.0, ts[0])
+        self.assertEqual(23.0, ts[1])
+        self.assertEqual(3.0, ts[2])
+        self.assertEqual(4.0, ts[3])
+
 
 class TestAggregatedTimeSerie(base.BaseTestCase):
     @staticmethod