diff --git a/libcxx/docs/BuildingLibcxx.rst b/libcxx/docs/BuildingLibcxx.rst
--- a/libcxx/docs/BuildingLibcxx.rst
+++ b/libcxx/docs/BuildingLibcxx.rst
@@ -166,7 +166,7 @@
 
 .. option:: LIBCXX_ENABLE_ASSERTIONS:BOOL
 
-  **Default**: ``ON``
+  **Default**: ``OFF``
 
   Build libc++ with assertions enabled.