diff --git a/test/test_conventions.py b/test/test_conventions.py
index 2c0ac26eb23..ae13a5ff0e0 100644
--- a/test/test_conventions.py
+++ b/test/test_conventions.py
@@ -2,7 +2,7 @@
 import pandas as pd
 import warnings
 
-from xray import conventions
+from xray import conventions, Dataset
 from . import TestCase, requires_netCDF4
 
 
@@ -139,6 +139,27 @@ def test_slice_decoded_cf_datetime_array(self):
         self.assertEqual(actual.dtype, np.dtype('datetime64[ns]'))
         self.assertArrayEqual(actual[[0, 2]], expected[[0, 2]])
 
+    @requires_netCDF4
+    def test_decode_cf_variable(self):
+        ds = Dataset({'time': ('time', [0, 1, 2],
+                               {'units': 'days since 1900-01-01',
+                                'calendar': 'standard'})})
+        actual = conventions.decode_cf_variable(ds['time'])
+        expected = pd.date_range('1900-01-01', periods=3).values
+        self.assertEqual(actual.dtype, np.dtype('datetime64[ns]'))
+        self.assertArrayEqual(actual.values, expected)
+
+        actual = conventions.decode_cf_variable(ds['time'].variable)
+        self.assertEqual(actual.dtype, np.dtype('datetime64[ns]'))
+        self.assertArrayEqual(actual.values, expected)
+
+        # default calendar
+        ds = Dataset({'time': ('time', [0, 1, 2],
+                               {'units': 'days since 1900-01-01'})})
+        actual = conventions.decode_cf_variable(ds['time'])
+        self.assertEqual(actual.dtype, np.dtype('datetime64[ns]'))
+        self.assertArrayEqual(actual.values, expected)
+
     @requires_netCDF4
     def test_decode_non_standard_calendar(self):
         import netCDF4 as nc4
diff --git a/xray/conventions.py b/xray/conventions.py
index 7ea7bd33765..69ad682289c 100644
--- a/xray/conventions.py
+++ b/xray/conventions.py
@@ -413,7 +413,8 @@ def get_to(source, dest, k):
 
 def decode_cf_variable(var, concat_characters=True, mask_and_scale=True,
                        decode_times=True):
-    # use _data instead of data so as not to trigger loading data
+    var = xray.variable.as_variable(var)
+    # use _data instead of values so as not to trigger loading data
     data = var._data
     dimensions = var.dimensions
     attributes = var.attrs.copy()
@@ -433,7 +434,7 @@ def pop_to(source, dest, k):
         return v
 
     if 'dtype' in encoding:
-        if var.data.dtype != encoding['dtype']:
+        if data.dtype != encoding['dtype']:
             raise ValueError("Refused to overwrite dtype")
     encoding['dtype'] = data.dtype