Operating system: Window 7 SP1
Graphics card: nVidia 660 GTX
version: 2.80 (sub 74), branch: blender2.7, commit date: 2019-06-09 21:43, hash: 030c7df19da9, type: Release
build date: 09/06/2019, 17:18
Short description of error
Alpha of rendered transparent workbench image is wrong.
Exact steps for others to reproduce the error
Open the default scene and look through the camera. Change the render engine to "Workbench" and activate the Transparent flag under the Film rollout.
Render the scene, inspect the pixels and you will discover that the alpha of the pixels of the cube are not entirely solid, as they should be.