diff --git a/src/display_buffer.cc b/src/display_buffer.cc
index 5b8aaff3..ac2bb593 100644
--- a/src/display_buffer.cc
+++ b/src/display_buffer.cc
@@ -12,8 +12,8 @@ DisplayLine::iterator DisplayLine::split(iterator it, BufferIterator pos)
     assert(it->content.end() > pos);
 
     DisplayAtom atom = *it;
-    atom.content.end() = pos;
-    it->content.begin() = pos;
+    atom.content.m_end = pos;
+    it->content.m_begin = pos;
     return m_atoms.insert(it, std::move(atom));
 }
 
diff --git a/src/display_buffer.hh b/src/display_buffer.hh
index 2b3fcc0e..e1f1442f 100644
--- a/src/display_buffer.hh
+++ b/src/display_buffer.hh
@@ -32,6 +32,8 @@ enum Attributes
     Bold = 8
 };
 
+class DisplayLine;
+
 struct AtomContent
 {
 public:
@@ -69,13 +71,13 @@ public:
         }
     }
 
-    BufferIterator& begin()
+    const BufferIterator& begin() const
     {
         assert(has_buffer_range());
         return m_begin;
     }
 
-    BufferIterator& end()
+    const BufferIterator& end() const
     {
         assert(has_buffer_range());
         return m_end;
@@ -96,6 +98,8 @@ public:
     Type type() const { return m_type; }
 
 private:
+    friend class DisplayLine;
+
     Type m_type;
 
     BufferIterator m_begin;