diff --git a/lib/iris/tests/results/merge/separable_combination.cml b/lib/iris/tests/results/merge/separable_combination.cml
index 0b95263afc..11ac2989fe 100644
--- a/lib/iris/tests/results/merge/separable_combination.cml
+++ b/lib/iris/tests/results/merge/separable_combination.cml
@@ -5,7 +5,7 @@
       <coord datadims="[0]">
         <auxCoord id="78c32bc2" long_name="a" points="[2005, 2005, 2005, 2026, 2026, 2026, 2002, 2002,
 		2002, 2002, 2002, 2002, 2502, 2502, 2502, 2502,
-		2502, 2502, 2502, 2502, 2502]" shape="(21,)" units="Unit('1')" value_type="string"/>
+		2502, 2502, 2502, 2502, 2502]" shape="(21,)" units="Unit('1')" value_type="unicode"/>
       </coord>
       <coord datadims="[0]">
         <auxCoord id="414e1707" long_name="b" points="[ECMWF, ECMWF, ECMWF, UK Met Office,
@@ -13,7 +13,7 @@
 		CERFACS, IFM-GEOMAR, IFM-GEOMAR, IFM-GEOMAR,
 		UK Met Office, UK Met Office, UK Met Office,
 		UK Met Office, UK Met Office, UK Met Office,
-		UK Met Office, UK Met Office, UK Met Office]" shape="(21,)" units="Unit('1')" value_type="string"/>
+		UK Met Office, UK Met Office, UK Met Office]" shape="(21,)" units="Unit('1')" value_type="unicode"/>
       </coord>
       <coord datadims="[0]">
         <auxCoord id="56350344" long_name="c" points="[HOPE-E, Sys 1, Met 1, ENSEMBLES,
@@ -36,7 +36,7 @@
 		HadCM3, Sys 51, Met 15, ENSEMBLES,
 		HadCM3, Sys 51, Met 16, ENSEMBLES,
 		HadCM3, Sys 51, Met 17, ENSEMBLES,
-		HadCM3, Sys 51, Met 18, ENSEMBLES]" shape="(21,)" units="Unit('1')" value_type="string"/>
+		HadCM3, Sys 51, Met 18, ENSEMBLES]" shape="(21,)" units="Unit('1')" value_type="unicode"/>
       </coord>
       <coord datadims="[0]">
         <auxCoord id="32546e8d" long_name="d" points="[0.0, 1.0, 2.0, 0.0, 1.0, 2.0, 0.0, 1.0, 2.0,
diff --git a/lib/iris/tests/test_merge.py b/lib/iris/tests/test_merge.py
index dd8683b4b4..f19b2cc979 100644
--- a/lib/iris/tests/test_merge.py
+++ b/lib/iris/tests/test_merge.py
@@ -194,7 +194,8 @@ def _make_cube(self, a, b, c, d, data=0):
                                     long_name='y', units='1'), 0)
 
         for name, value in zip(['a', 'b', 'c', 'd'], [a, b, c, d]):
-            dtype = np.str if isinstance(value, six.string_types) else np.float32
+            dtype = (np.dtype(six.text_type)
+                     if isinstance(value, six.string_types) else np.float32)
             cube.add_aux_coord(AuxCoord(np.array([value], dtype=dtype),
                                         long_name=name, units='1'))