diff --git a/CI.md b/CI.md
index cbe0bdfa4fd..10ec108084b 100644
--- a/CI.md
+++ b/CI.md
@@ -35,7 +35,7 @@
 9. Special build check
     - ???
 10. Compatibility check
-    - ???
+    - Checks that `clickhouse` binary runs on distros with old libc versions.
 11. AST fuzzer
 12. Functional stateful tests
 13. Functional stateless tests