diff --git a/compiler-rt/www/index.html b/compiler-rt/www/index.html
--- a/compiler-rt/www/index.html
+++ b/compiler-rt/www/index.html
@@ -129,7 +129,9 @@
 
   <p>Tests for sanitizer runtimes are ported to
   <a href="https://llvm.org/docs/CommandGuide/lit.html">llvm-lit</a> and are
-  run by <b>make check-all</b> command in LLVM/Clang/compiler-rt build tree.</p>
+  run by <b>make check-all</b> command in LLVM/Clang/compiler-rt build tree.
+  Note that to run the check-all target, clang also need to enabled with
+  -DLLVM_ENABLE_PROJECTS option.</p>
 
   <p>compiler-rt libraries are installed to the system with <b>make install</b>
   command in either LLVM/Clang/compiler-rt or standalone