diff --git a/src/option_manager.cc b/src/option_manager.cc
index 7c98daff..c510dff8 100644
--- a/src/option_manager.cc
+++ b/src/option_manager.cc
@@ -26,13 +26,13 @@ OptionManager::~OptionManager()
     kak_assert(m_watchers.empty());
 }
 
-void OptionManager::register_watcher(OptionManagerWatcher& watcher)
+void OptionManager::register_watcher(OptionManagerWatcher& watcher) const
 {
     kak_assert(not contains(m_watchers, &watcher));
     m_watchers.push_back(&watcher);
 }
 
-void OptionManager::unregister_watcher(OptionManagerWatcher& watcher)
+void OptionManager::unregister_watcher(OptionManagerWatcher& watcher) const
 {
     auto it = find(m_watchers.begin(), m_watchers.end(), &watcher);
     kak_assert(it != m_watchers.end());
diff --git a/src/option_manager.hh b/src/option_manager.hh
index d4d50daf..cff6f34f 100644
--- a/src/option_manager.hh
+++ b/src/option_manager.hh
@@ -91,8 +91,8 @@ public:
     using OptionList = Vector<const Option*>;
     OptionList flatten_options() const;
 
-    void register_watcher(OptionManagerWatcher& watcher);
-    void unregister_watcher(OptionManagerWatcher& watcher);
+    void register_watcher(OptionManagerWatcher& watcher) const;
+    void unregister_watcher(OptionManagerWatcher& watcher) const;
 
     void on_option_changed(const Option& option) override;
 private:
@@ -105,7 +105,7 @@ private:
     Vector<std::unique_ptr<Option>, MemoryDomain::Options> m_options;
     OptionManager* m_parent;
 
-    Vector<OptionManagerWatcher*, MemoryDomain::Options> m_watchers;
+    mutable Vector<OptionManagerWatcher*, MemoryDomain::Options> m_watchers;
 };
 
 template<typename T>