Problem resizing an image

After just setting up the backup service and running a snapshot, I tried to shrink an image (to make room for a dedicated dev image) and received the following error:

lv_resize: Image is currently snapshotted.

Furthermore, a quick df -h shows that the filesystem has been resized to the desired size, but on the dashboard it still shows the previous size. This means that the filesystem resize is successful but something is failing in the image resize. Any ideas?