diff --git a/fsl/data/imagewrapper.py b/fsl/data/imagewrapper.py
index 53b68cc35be6fa60f02bb1853aebf7d79c4803a8..591002f455a4afe01e5ca5e97add890f2e32790d 100644
--- a/fsl/data/imagewrapper.py
+++ b/fsl/data/imagewrapper.py
@@ -271,7 +271,7 @@ class ImageWrapper(notifier.Notifier):
                   array of shape ``(nd, 2)``, where ``nd`` is the number
                   of dimensions in the volume.
         """
-        return self.__coverage[..., vol]
+        return np.array(self.__coverage[..., vol], dtype=np.uint32)
 
     
     def loadData(self):