diff --git a/README.md b/README.md
index 8740162..12e11c2 100644
--- a/README.md
+++ b/README.md
@@ -62,3 +62,7 @@ As it stands:
 Code style:
 - Two space indent, brace on the same line, middle pointers - `char * p;`.
 
+## Show-stoppers
+
+clang bug (msys2 packages repository ticket 4958) - makes it impossible to
+build on x86_64 Windows with clang. Only gcc is supported.