**System Information**
Operating system: Linux-5.4.0-42-generic-x86_64-with-debian-buster-sid 64 Bits
Graphics card: GeForce GTX 1660 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 440.100
**Blender Version**
Broken: version: 2.91.0 Alpha, branch: master, commit date: 2020-08-06 17:52, hash: `rB9a1ff4445b98`
Worked: rB55401fbb3d0d
**Short description of error**
The material icons in the material slots have a black background instead of being transparent.
This behavior was introduced by rBda741013a1e1 (which is the first bad commit)
See attachments:
//General material slots: //
{F8753600}
//GPencil material slots: //
{F8753602}
**Exact steps for others to reproduce the error**
1. Open Blender
2. Select the Cube (if not already)
3. Change to the material tab
4. Edit a value (e.g. change the color) and wait a few seconds to update the preview icons
For Grease Pencil it is similar if you
1. Open Blender
2. Select //2D Animation// on the //Splash Screen//
3. Change to the material tab
4. Edit a value (e.g. change the color) and wait a few seconds to update the preview icon
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Have a nice mice 😅