diff --git a/nova/tests/test_xenapi.py b/nova/tests/test_xenapi.py
index 4a971ff21d3..f8b0c17910c 100644
--- a/nova/tests/test_xenapi.py
+++ b/nova/tests/test_xenapi.py
@@ -139,6 +139,28 @@ def _make_info():
             }
         }
 
+    def test_mountpoint_to_number(self):
+        cases = {
+            'sda': 0,
+            'sdp': 15,
+            'hda': 0,
+            'hdp': 15,
+            'vda': 0,
+            'xvda': 0,
+            '0': 0,
+            '10': 10,
+            'vdq': -1,
+            'sdq': -1,
+            'hdq': -1,
+            'xvdq': -1,
+        }
+
+        for (input, expected) in cases.iteritems():
+            func = volume_utils.VolumeHelper.mountpoint_to_number
+            actual = func(input)
+            self.assertEqual(actual, expected,
+                    '%s yielded %s, not %s' % (input, actual, expected))
+
     def test_parse_volume_info_raise_exception(self):
         """This shows how to test helper classes' methods."""
         stubs.stubout_session(self.stubs, stubs.FakeSessionForVolumeTests)
diff --git a/nova/virt/xenapi/volume_utils.py b/nova/virt/xenapi/volume_utils.py
index e8124f7efb3..da1921bad0d 100644
--- a/nova/virt/xenapi/volume_utils.py
+++ b/nova/virt/xenapi/volume_utils.py
@@ -357,8 +357,8 @@ def mountpoint_to_number(cls, mountpoint):
             mountpoint = mountpoint[5:]
         if re.match('^[hs]d[a-p]$', mountpoint):
             return (ord(mountpoint[2:3]) - ord('a'))
-        elif re.match('^vd[a-p]$', mountpoint):
-            return (ord(mountpoint[2:3]) - ord('a'))
+        elif re.match('^x?vd[a-p]$', mountpoint):
+            return (ord(mountpoint[-1]) - ord('a'))
         elif re.match('^[0-9]+$', mountpoint):
             return string.atoi(mountpoint, 10)
         else: