diff --git a/README.md b/README.md
index f12f3e9..9e26df8 100644
--- a/README.md
+++ b/README.md
@@ -48,3 +48,5 @@ Ensure to use a clean cache if other repos have been used before, i.e. call `pak
 ## Lessons learned
 
 - Newer R versions have issues compiling C code from older package Versions. Using an older R version to build the binaries is recommended.
+- R 4.0.5 is used to build all binaries for R 4.x
+- Binaries which cannot be built using R 4.0.5 often also require older system library or compiler versions and are out of scope for this project.