diff --git a/src/buffer.cc b/src/buffer.cc
index 33f2ae3b..81e63b95 100644
--- a/src/buffer.cc
+++ b/src/buffer.cc
@@ -249,14 +249,14 @@ void Buffer::notify_saved()
     m_last_save_undo_index = history_cursor_index;
 }
 
-void Buffer::register_modification_listener(BufferModificationListener* listener) const
+void Buffer::register_modification_listener(BufferModificationListener* listener)
 {
     assert(listener);
     assert(not contains(m_modification_listeners, listener));
     m_modification_listeners.push_back(listener);
 }
 
-void Buffer::unregister_modification_listener(BufferModificationListener* listener) const
+void Buffer::unregister_modification_listener(BufferModificationListener* listener)
 {
     assert(listener);
     auto it = std::find(m_modification_listeners.begin(),
diff --git a/src/buffer.hh b/src/buffer.hh
index be0e0d47..35572a2d 100644
--- a/src/buffer.hh
+++ b/src/buffer.hh
@@ -146,8 +146,8 @@ public:
     Type type() const { return m_type; }
     void notify_saved();
 
-    void register_modification_listener(BufferModificationListener* listener) const;
-    void unregister_modification_listener(BufferModificationListener* listener) const;
+    void register_modification_listener(BufferModificationListener* listener);
+    void unregister_modification_listener(BufferModificationListener* listener);
 
 private:
     BufferChar at(BufferPos position) const;
@@ -180,7 +180,7 @@ private:
 
     size_t m_last_save_undo_index;
 
-    mutable std::vector<BufferModificationListener*> m_modification_listeners;
+    std::vector<BufferModificationListener*> m_modification_listeners;
 };
 
 }
diff --git a/src/dynamic_buffer_iterator.cc b/src/dynamic_buffer_iterator.cc
index 42c9d39c..fac3cd39 100644
--- a/src/dynamic_buffer_iterator.cc
+++ b/src/dynamic_buffer_iterator.cc
@@ -59,13 +59,13 @@ void DynamicBufferIterator::on_modification(const BufferModification& modificati
 void DynamicBufferIterator::register_ifp()
 {
     if (is_valid())
-        buffer().register_modification_listener(this);
+        const_cast<Buffer&>(buffer()).register_modification_listener(this);
 }
 
 void DynamicBufferIterator::unregister_ifn()
 {
     if (is_valid())
-        buffer().unregister_modification_listener(this);
+        const_cast<Buffer&>(buffer()).unregister_modification_listener(this);
 }
 
 }