Tooltip doesn't show up on mouse hover

Have been struggling with the following code for some time now. I am not sure why this is rendering any tooltips. What am I doing wrong here? Everything works except the tooltips.

xdr = Range1d(start=0, end=x_num*w+(padding*(x_num+2)))
ydr = Range1d(start=y_num*h+(padding*(y_num+2)), end=0)

plot = Plot(
    title=None, x_range=xdr, y_range=ydr, plot_width=x_num*w, plot_height=y_num*h,
    min_border=0, toolbar_location=None)

image = ImageURL(url="url", x="x", y="y", w="w", h="h", anchor="top_left")
plot.add_glyph(source, image)

plot.add_tools(HoverTool(tooltips=TOOLTIPS))

curdoc().add_root(plot)

show(plot)

ImageURL does not currently support any kinds of hit-testing:

Is it possible to wrap the image url inside some other element and then do it?

You could certainly plot invisible circles (or any other glyph) at the same x, y positions and use those to drive a hover tool.