What's wrong with my screenshot function?

setupScript.screenshot = new Texture2D(Screen.width,Screen.height,TextureFormat.RGB24,false);
yield new WaitForEndOfFrame(); // to ward off a “…while not in drawing frame” error
setupScript.screenshot.ReadPixels(Rect(0,0,Screen.width,Screen.height),0,0,false);

I paused the game and checked out SetupScript’s “screenshot” variable in the inspector right after this
was called. It is a gray rectangle. The proportions are right, but the content is nothing but flat light gray.

I assume you’ve seen this: Unity - Scripting API: Texture2D.ReadPixels

Do you ever call ‘Apply’ as in setupScript.screenshot.Apply() ?