diff --git a/llvm/docs/CommandGuide/llvm-cxxfilt.rst b/llvm/docs/CommandGuide/llvm-cxxfilt.rst
--- a/llvm/docs/CommandGuide/llvm-cxxfilt.rst
+++ b/llvm/docs/CommandGuide/llvm-cxxfilt.rst
@@ -52,10 +52,15 @@
 
   Print an uncategorized summary of command line options.
 
+.. option:: --no-strip-underscore, -n
+
+  Do not strip a leading underscore. This is the default for all platforms
+  except Mach-O based hosts.
+
 .. option:: --strip-underscore, -_
 
-  Discard a single leading underscore, if present, from each input name before
-  demangling.
+  Strip a single leading underscore, if present, from each input name before
+  demangling. On by default on Mach-O based platforms.
 
 .. option:: --types, -t