diff --git a/ext/libraries/zkgroup/README.md b/ext/libraries/zkgroup/README.md
index eef4615..69d9c59 100644
--- a/ext/libraries/zkgroup/README.md
+++ b/ext/libraries/zkgroup/README.md
@@ -9,3 +9,7 @@
   run `cross build --target aarch64-unknown-linux-gnu --release`
 to build the library for `x86-64`, `armv7` and `arm64`
 * the built library will be in the `target/<architecture>/release` folder 
+
+## Why?
+
+Building zkgroup every time a new docker image gets released takes really long (especially for cross platform builds with docker/buildx and QEMU). Furthermore, due to this bug here (https://github.com/docker/buildx/issues/395) we would need to use an ugly workaround for that right now. As zkgroup isn't released very often I guess it's okay to manually build a new version once in a while.