diff --git a/lib/iris/cube.py b/lib/iris/cube.py
index c04518f886..b77850afb8 100644
--- a/lib/iris/cube.py
+++ b/lib/iris/cube.py
@@ -836,7 +836,13 @@ def add_dim_coord(self, dim_coord, data_dim):
 
     def _add_unique_dim_coord(self, dim_coord, data_dim):
         if isinstance(dim_coord, iris.coords.AuxCoord):
-            raise ValueError('The dim_coord may not be an AuxCoord instance.')
+            try:
+                dim_coord = iris.coords.DimCoord.from_coord(dim_coord)
+                warnings.warn('converting AuxCoord to DimCoord',
+                              stacklevel=2)
+            except ValueError as e:
+                raise ValueError('Could not convert coord to DimCoord. '
+                                 + str(e))
 
         # Convert data_dim to a single integer
         if isinstance(data_dim, collections.Container):
diff --git a/lib/iris/tests/test_cube.py b/lib/iris/tests/test_cube.py
index f8f0549e9b..6de21a5631 100644
--- a/lib/iris/tests/test_cube.py
+++ b/lib/iris/tests/test_cube.py
@@ -1,4 +1,4 @@
-# (C) British Crown Copyright 2010 - 2013, Met Office
+# (C) British Crown Copyright 2010 - 2014, Met Office
 #
 # This file is part of Iris.
 #
@@ -81,11 +81,17 @@ def test_no_dim(self):
                           self.cube.add_dim_coord,
                           iris.coords.DimCoord(np.arange(2), "latitude"))
 
-    def test_adding_aux_coord(self):
-        coord = iris.coords.AuxCoord(np.arange(2), "latitude")
+    def test_adding_nonmonotonic_aux_coord(self):
+        coord = iris.coords.AuxCoord([0, 1, 1, 2], "latitude")
         with self.assertRaises(ValueError):
             self.cube.add_dim_coord(coord, 0)
 
+    def test_adding_aux_coord(self):
+        coord = iris.coords.AuxCoord(np.arange(2), "latitude")
+        self.cube.add_dim_coord(coord, 0)
+        self.assertIsInstance(self.cube.coord("latitude"),
+                              iris.coords.DimCoord)
+
 
 class TestEquality(tests.IrisTest):
     def test_not_implmemented(self):