diff --git a/src/buffer.cc b/src/buffer.cc
index f3283d20..08c27796 100644
--- a/src/buffer.cc
+++ b/src/buffer.cc
@@ -37,17 +37,6 @@ Buffer::~Buffer()
     assert(m_modification_listeners.empty());
 }
 
-void Buffer::erase(const BufferIterator& begin, const BufferIterator& end)
-{
-    append_modification(Modification(Modification::Erase, begin,
-                                     string(begin, end)));
-}
-
-void Buffer::insert(const BufferIterator& position, const BufferString& string)
-{
-    append_modification(Modification(Modification::Insert, position, string));
-}
-
 BufferIterator Buffer::iterator_at(const BufferCoord& line_and_column) const
 {
     if (m_lines.empty())
@@ -227,7 +216,7 @@ void Buffer::apply_modification(const Modification& modification)
         listener->on_modification(modification);
 }
 
-void Buffer::append_modification(Modification&& modification)
+void Buffer::modify(Modification&& modification)
 {
     for (auto filter : m_filters)
         filter.second(*this, modification);
diff --git a/src/buffer.hh b/src/buffer.hh
index 4ac11627..eb4c5c67 100644
--- a/src/buffer.hh
+++ b/src/buffer.hh
@@ -86,10 +86,14 @@ struct Modification
     BufferString   content;
 
     Modification(Type type, BufferIterator position,
-                       BufferString content)
+                 const BufferString& content)
         : type(type), position(position), content(content) {}
 
     Modification inverse() const;
+
+    static Modification make_erase(BufferIterator begin, BufferIterator end);
+    static Modification make_insert(BufferIterator position,
+                                    const BufferString& content);
 };
 
 class ModificationListener
@@ -117,15 +121,11 @@ public:
     void           begin_undo_group();
     void           end_undo_group();
 
+    void           modify(Modification&& modification);
+
     bool           undo();
     bool           redo();
 
-    void           erase(const BufferIterator& begin,
-                         const BufferIterator& end);
-
-    void           insert(const BufferIterator& position,
-                          const BufferString& string);
-
     BufferString   string(const BufferIterator& begin,
                           const BufferIterator& end) const;
 
@@ -200,8 +200,6 @@ private:
     void apply_modification(const Modification& modification);
     void revert_modification(const Modification& modification);
 
-    void append_modification(Modification&& modification);
-
     std::list<std::unique_ptr<Window>> m_windows;
 
     size_t m_last_save_undo_index;
@@ -211,6 +209,18 @@ private:
     idvaluemap<std::string, FilterFunc> m_filters;
 };
 
+inline Modification Modification::make_erase(BufferIterator begin,
+                                             BufferIterator end)
+{
+    return Modification(Erase, begin, begin.buffer().string(begin, end));
+}
+
+inline Modification Modification::make_insert(BufferIterator position,
+                                              const BufferString& content)
+{
+    return Modification(Insert, position, content);
+}
+
 }
 
 #include "buffer_iterator.inl.hh"
diff --git a/src/debug.cc b/src/debug.cc
index 8fbc5b41..4fe802bf 100644
--- a/src/debug.cc
+++ b/src/debug.cc
@@ -21,7 +21,7 @@ static Buffer& get_or_create_debug_buffer()
 void write_debug(const std::string& str)
 {
     Buffer& debug_buffer = get_or_create_debug_buffer();
-    debug_buffer.insert(debug_buffer.end()-1, str);
+    debug_buffer.modify(Modification::make_insert(debug_buffer.end()-1, str));
 }
 
 }
diff --git a/src/window.cc b/src/window.cc
index c0207cc7..0cf0fbef 100644
--- a/src/window.cc
+++ b/src/window.cc
@@ -90,7 +90,7 @@ void Window::erase_noundo()
 {
     check_invariant();
     for (auto& sel : m_selections)
-        m_buffer.erase(sel.begin(), sel.end());
+        m_buffer.modify(Modification::make_erase(sel.begin(), sel.end()));
     scroll_to_keep_cursor_visible_ifn();
 }
 
@@ -126,7 +126,7 @@ void Window::insert(const String& string)
 void Window::insert_noundo(const String& string)
 {
     for (auto& sel : m_selections)
-        m_buffer.insert(sel.begin(), string);
+        m_buffer.modify(Modification::make_insert(sel.begin(), string));
     scroll_to_keep_cursor_visible_ifn();
 }
 
@@ -139,7 +139,7 @@ void Window::append(const String& string)
 void Window::append_noundo(const String& string)
 {
     for (auto& sel : m_selections)
-        m_buffer.insert(sel.end(), string);
+        m_buffer.modify(Modification::make_insert(sel.end(), string));
     scroll_to_keep_cursor_visible_ifn();
 }
 
@@ -394,14 +394,14 @@ IncrementalInserter::IncrementalInserter(Window& window, Mode mode)
         case Mode::AppendAtLineEnd:
             pos = m_window.m_buffer.iterator_at_line_end(sel.end() - 1) - 1;
             if (mode == Mode::OpenLineBelow)
-                window.m_buffer.insert(pos, "\n");
+                window.m_buffer.modify(Modification::make_insert(pos, "\n"));
             break;
 
         case Mode::OpenLineAbove:
         case Mode::InsertAtLineBegin:
             pos = m_window.m_buffer.iterator_at_line_begin(sel.begin());
             if (mode == Mode::OpenLineAbove)
-                window.m_buffer.insert(--pos, "\n");
+                window.m_buffer.modify(Modification::make_insert(--pos, "\n"));
             break;
         }
         sel = Selection(pos, pos, sel.captures());
@@ -425,7 +425,8 @@ void IncrementalInserter::insert(const Window::String& string)
 void IncrementalInserter::insert_capture(size_t index)
 {
     for (auto& sel : m_window.m_selections)
-        m_window.m_buffer.insert(sel.begin(), sel.capture(index));
+        m_window.m_buffer.modify(Modification::make_insert(sel.begin(),
+                                                           sel.capture(index)));
     m_window.scroll_to_keep_cursor_visible_ifn();
 }