diff --git a/lib/iris/_lazy_data.py b/lib/iris/_lazy_data.py
index a3f2b7a13c..1b3124a457 100644
--- a/lib/iris/_lazy_data.py
+++ b/lib/iris/_lazy_data.py
@@ -100,9 +100,10 @@ def array_masked_to_nans(array):
     if not ma.isMaskedArray(array):
         result = array
     else:
-        if array.dtype.kind == 'i':
-            array = array.astype(np.dtype('f8'))
-        mask = array.mask
-        array[mask] = np.nan
+        if ma.is_masked(array):
+            if array.dtype.kind == 'i':
+                array = array.astype(np.dtype('f8'))
+            mask = array.mask
+            array[mask] = np.nan
         result = array.data
     return result
diff --git a/lib/iris/tests/unit/lazy_data/test_array_masked_to_nans.py b/lib/iris/tests/unit/lazy_data/test_array_masked_to_nans.py
index e3c94bfb8c..b536b78c3a 100644
--- a/lib/iris/tests/unit/lazy_data/test_array_masked_to_nans.py
+++ b/lib/iris/tests/unit/lazy_data/test_array_masked_to_nans.py
@@ -89,12 +89,12 @@ def test_unmasked__integers(self):
         self.assertIs(result, unmasked_array)
 
     def test_no_mask__integers(self):
-        masked_array = ma.masked_array([1, 2], mask=ma.nomask)
+        masked_array = ma.masked_array([1, 2], dtype=np.int16, mask=ma.nomask)
 
         result = array_masked_to_nans(masked_array)
 
         self._common_checks(result)
-        self.assertEqual(result.dtype, np.dtype('f8'))
+        self.assertEqual(result.dtype, np.dtype('i2'))
 
 
 if __name__ == '__main__':