diff --git a/src/main/cpp/option_processor.h b/src/main/cpp/option_processor.h
index 5cb4ed3..bfe2070 100644
--- a/src/main/cpp/option_processor.h
+++ b/src/main/cpp/option_processor.h
@@ -105,6 +105,8 @@
   // Gets the arguments explicitly provided by the user's command line.
   std::vector<std::string> GetExplicitCommandArguments() const;
 
+  // Returns the underlying StartupOptions object with parsed values. Must
+  // only be called after ParseOptions.
   virtual StartupOptions* GetParsedStartupOptions() const;
 
   // Prints a message about the origin of startup options. This should be called
@@ -145,9 +147,12 @@
 
   const WorkspaceLayout* workspace_layout_;
 
-  // The startup options parsed from args, this field is initialized by
-  // ParseOptions.
-  std::unique_ptr<StartupOptions> parsed_startup_options_;
+  // The StartupOptions object defining the startup options which are accepted,
+  // and, after ParseOptions has been called, their values.
+  const std::unique_ptr<StartupOptions> startup_options_;
+
+  // Whether or not ParseOptions has been called.
+  bool parse_options_called_;
 
   // Path to the system-wide bazelrc configuration file.
   // This is configurable for testing purposes only.