diff --git a/llvm/include/llvm/Support/CommandLine.h b/llvm/include/llvm/Support/CommandLine.h
index c36373520676..70465a0e3fd3 100644
--- a/llvm/include/llvm/Support/CommandLine.h
+++ b/llvm/include/llvm/Support/CommandLine.h
@@ -1733,7 +1733,7 @@ void PrintHelpMessage(bool Hidden = false, bool Categorized = false);
 /// Hopefully this API can be depricated soon. Any situation where options need
 /// to be modified by tools or libraries should be handled by sane APIs rather
 /// than just handing around a global list.
-StringMap<Option *> &getRegisteredOptions(SubCommand &Sub);
+StringMap<Option *> &getRegisteredOptions(SubCommand &Sub = *TopLevelSubCommand);
 
 //===----------------------------------------------------------------------===//
 // Standalone command line processing utilities.