# Why is my Canvas/RawImage not included in my Camera's RenderTexture output?

In my Unity2D game, I'm using a second camera to "screenshot" the current view. I then display this screenshot within the game. This works the first time I take a screenshot. When taking the second screenshot, I expect the first screenshot to show up in the second, creating a screenshot-within-a-screenshot effect. However, this doesn't happen - the previous screenshot doesn't show up in the next.

Here's a more visual description:

Before taking any screenshots:

After taking the first screenshot and displaying it in the bottom-left corner:

After taking the second screenshot:

Notice that this screenshot looks identical to the previous one. Here's what I expected:

It seems like my Canvas/RawImage that is displaying the screenshot isn't being captured by my second camera. Why is this?

Some additional details: my canvas is set to Screen Space - Camera. I'm using Unity 5.6.1f1.

UPDATE: Upon opening up this test project another day, this seems to be broken once again (even with my Canvas set to World Space). I'm suspecting this might be a bug with Unity, and I've filed a bug report. I'll update this answer once I hear back from Unity.
Figured it out while posting, but in the spirit of Stack Exchange, I'll post my question with the solution. I just had to switch my Canvas's render mode to World Space: