diff --git a/.github/workflows/compilers.yml b/.github/workflows/compilers.yml
index 26c6d3589c..cb87c6601d 100644
--- a/.github/workflows/compilers.yml
+++ b/.github/workflows/compilers.yml
@@ -93,6 +93,7 @@ jobs:
           - { name: clang-12,  env: { default_cc: clang-12 } }
           - { name: clang-11,  env: { default_cc: clang-11 } }
           - { name: clang-10,  env: { default_cc: clang-10 } }
+          # llvm-objcopy<=9 doesn't have --wildcard. It compiles, but leaves Rust symbols in libyjit.o.
           - { name: clang-9,   env: { default_cc: clang-9,   append_configure: '--disable-yjit' } }
           - { name: clang-8,   env: { default_cc: clang-8,   append_configure: '--disable-yjit' } }
           - { name: clang-7,   env: { default_cc: clang-7,   append_configure: '--disable-yjit' } }