**System Information**
Operating system: Windows-10-10.0.18362-SP0 64 Bits
Graphics card: GeForce RTX 2060/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 442.23
**Blender Version**
Broken: version: 2.91.0 Alpha, branch: master, commit date: 2020-10-15 08:00, hash: `rBf1aa55b6e9cd`
**Short description of error**
See screenshot below. Expected result: the circled viewer shows the cube silhouette in red. Instead we see solid red output
{F9429282}
When the output of the set alpha node is connected to the composite node the viewer does display the expected result.
{F9429298}