diff --git a/include/llvm/System/Path.h b/include/llvm/System/Path.h
index ee3b5f6..23b18d4 100644
--- a/include/llvm/System/Path.h
+++ b/include/llvm/System/Path.h
@@ -164,6 +164,7 @@
 
       /// GetMainExecutable - Return the path to the main executable, given the
       /// value of argv[0] from program startup and the address of main itself.
+      /// In extremis, this function may fail and return an empty path.
       static Path GetMainExecutable(const char *argv0, void *MainAddr);
 
       /// This is one of the very few ways in which a path can be constructed