diff --git a/src/node_options-inl.h b/src/node_options-inl.h
index 8aaa62524b8ee6..d25557e6a50637 100644
--- a/src/node_options-inl.h
+++ b/src/node_options-inl.h
@@ -201,7 +201,7 @@ auto OptionsParser<Options>::Convert(
 template <typename Options>
 template <typename ChildOptions>
 void OptionsParser<Options>::Insert(
-    OptionsParser<ChildOptions>* child_options_parser,
+    const OptionsParser<ChildOptions>* child_options_parser,
     ChildOptions* (Options::* get_child)()) {
   aliases_.insert(child_options_parser->aliases_.begin(),
                   child_options_parser->aliases_.end());
@@ -274,7 +274,7 @@ void OptionsParser<Options>::Parse(
     std::vector<std::string>* const v8_args,
     Options* const options,
     OptionEnvvarSettings required_env_settings,
-    std::vector<std::string>* const errors) {
+    std::vector<std::string>* const errors) const {
   ArgsInfo args(orig_args, exec_args);
 
   // The first entry is the process name. Make sure it ends up in the V8 argv,
diff --git a/src/node_options.cc b/src/node_options.cc
index ef80971461455b..d665bc40400071 100644
--- a/src/node_options.cc
+++ b/src/node_options.cc
@@ -88,7 +88,7 @@ DebugOptionsParser::DebugOptionsParser() {
 }
 
 #if HAVE_INSPECTOR
-DebugOptionsParser DebugOptionsParser::instance;
+const DebugOptionsParser DebugOptionsParser::instance;
 #endif  // HAVE_INSPECTOR
 
 EnvironmentOptionsParser::EnvironmentOptionsParser() {
@@ -218,7 +218,7 @@ EnvironmentOptionsParser::EnvironmentOptionsParser() {
 #endif  // HAVE_INSPECTOR
 }
 
-EnvironmentOptionsParser EnvironmentOptionsParser::instance;
+const EnvironmentOptionsParser EnvironmentOptionsParser::instance;
 
 PerIsolateOptionsParser::PerIsolateOptionsParser() {
   AddOption("--track-heap-objects",
@@ -241,7 +241,7 @@ PerIsolateOptionsParser::PerIsolateOptionsParser() {
          &PerIsolateOptions::get_per_env_options);
 }
 
-PerIsolateOptionsParser PerIsolateOptionsParser::instance;
+const PerIsolateOptionsParser PerIsolateOptionsParser::instance;
 
 PerProcessOptionsParser::PerProcessOptionsParser() {
   AddOption("--title",
@@ -345,7 +345,7 @@ PerProcessOptionsParser::PerProcessOptionsParser() {
          &PerProcessOptions::get_per_isolate_options);
 }
 
-PerProcessOptionsParser PerProcessOptionsParser::instance;
+const PerProcessOptionsParser PerProcessOptionsParser::instance;
 
 inline std::string RemoveBrackets(const std::string& host) {
   if (!host.empty() && host.front() == '[' && host.back() == ']')
diff --git a/src/node_options.h b/src/node_options.h
index 816243345dcdae..d317e12b6f0db8 100644
--- a/src/node_options.h
+++ b/src/node_options.h
@@ -275,7 +275,7 @@ class OptionsParser {
   // a method that yields the target options type from this parser's options
   // type.
   template <typename ChildOptions>
-  void Insert(OptionsParser<ChildOptions>* child_options_parser,
+  void Insert(const OptionsParser<ChildOptions>* child_options_parser,
               ChildOptions* (Options::* get_child)());
 
   // Parse a sequence of options into an options struct, a list of
@@ -300,7 +300,7 @@ class OptionsParser {
                      std::vector<std::string>* const v8_args,
                      Options* const options,
                      OptionEnvvarSettings required_env_settings,
-                     std::vector<std::string>* const errors);
+                     std::vector<std::string>* const errors) const;
 
  private:
   // We support the wide variety of different option types by remembering
@@ -391,28 +391,28 @@ class DebugOptionsParser : public OptionsParser<DebugOptions> {
  public:
   DebugOptionsParser();
 
-  static DebugOptionsParser instance;
+  static const DebugOptionsParser instance;
 };
 
 class EnvironmentOptionsParser : public OptionsParser<EnvironmentOptions> {
  public:
   EnvironmentOptionsParser();
 
-  static EnvironmentOptionsParser instance;
+  static const EnvironmentOptionsParser instance;
 };
 
 class PerIsolateOptionsParser : public OptionsParser<PerIsolateOptions> {
  public:
   PerIsolateOptionsParser();
 
-  static PerIsolateOptionsParser instance;
+  static const PerIsolateOptionsParser instance;
 };
 
 class PerProcessOptionsParser : public OptionsParser<PerProcessOptions> {
  public:
   PerProcessOptionsParser();
 
-  static PerProcessOptionsParser instance;
+  static const PerProcessOptionsParser instance;
 };
 
 }  // namespace options_parser