diff --git a/lua/commonmarker/init.lua b/lua/commonmarker/init.lua
index e235009..de2d1a8 100644
--- a/lua/commonmarker/init.lua
+++ b/lua/commonmarker/init.lua
@@ -25,7 +25,6 @@ end
 
 local function byte2pos (byte)
 	local line = call_function("byte2line", { byte })
-	-- local col = byte - vim.api.nvim_buf_get_offset(buffer, line)
 	local col = byte - call_function("line2byte", { line })
 	return line, col
 end
@@ -36,9 +35,11 @@ local function get_contents (buffer)
 	return table.concat(lines)
 end
 
-local function highlight (buffer, namespace)
+local function highlight (buffer, namespace, firstline, lastline)
 	local contents = get_contents(buffer)
-	local events = rust.get_offsets(contents)
+	local firstbyte = call_function("line2byte", { firstline })
+	local lastbyte = call_function("line2byte", { lastline + 1 }) - 1
+	local events = rust.get_offsets(contents, firstbyte, lastbyte)
 	for _, event in ipairs(events) do
 		local sline, scol = byte2pos(event.first)
 		local eline, ecol = byte2pos(event.last)
@@ -57,7 +58,6 @@ local function highlight (buffer, namespace)
 end
 
 function commonmarker:detach (buffer)
-	dump(self._attachments)
 	self._attachments[buffer] = nil
 	buf_clear_namespace(buffer, self._namespace, 0, -1)
 end
@@ -65,14 +65,13 @@ end
 function commonmarker:attach (buffer)
 	if self._attachments[buffer] then return end
 	self._attachments[buffer] = true
-	highlight(buffer, self._namespace)
+	highlight(buffer, self._namespace, 1, call_function("line", { "$" }))
 	buf_attach(buffer, false, {
-			on_lines = function (_, _, _, _, _, _)
-				dump(self)
-				buf_clear_namespace(buffer, self._namespace, 0, -1)
+			on_lines = function (_, _, _, firstline, lastline, _)
+				buf_clear_namespace(buffer, self._namespace, firstline, lastline)
 				-- Returning true here detaches, we thought we should have been already
 				if not self._attachments[buffer] then return true end
-				highlight(buffer, self._namespace)
+				highlight(buffer, self._namespace, firstline, lastline)
 			end,
 			on_detach = function (_)
 				self._attachments[buffer] = nil
diff --git a/src/lib.rs b/src/lib.rs
index e2e9e68..e630d00 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -27,7 +27,7 @@ struct MdTag {
 
 type Events = Vec<MdTag>;
 
-fn get_offsets(buffer: String) -> Result<Events> {
+fn get_offsets(buffer: String, firstbyte: usize, lastbyte: usize) -> Result<Events> {
     let options = Options::all();
     let parser = Parser::new_ext(buffer.as_str(), options);
     let mut events = Events::new();
@@ -35,6 +35,9 @@ fn get_offsets(buffer: String) -> Result<Events> {
         let first = range.start + 1;
         let last = range.end + 1;
         let mut lang = None;
+        if firstbyte > last || lastbyte < first {
+            continue;
+        }
         let group = match event {
             Event::Start(tag) => match tag {
                 Tag::Heading(level) => Some(format!("cmarkHeading{}", level)),
diff --git a/src/lua.rs b/src/lua.rs
index bfc4fce..63444f3 100644
--- a/src/lua.rs
+++ b/src/lua.rs
@@ -5,9 +5,12 @@ fn to_html(_: &Lua, buffer: String) -> LuaResult<String> {
     Ok(super::to_html(buffer).unwrap())
 }
 
-fn get_offsets(lua: &Lua, buffer: String) -> LuaResult<LuaTable> {
+fn get_offsets(
+    lua: &Lua,
+    (buffer, firstbyte, lastbyte): (String, usize, usize),
+) -> LuaResult<LuaTable> {
     let table = lua.create_table().unwrap();
-    let events = super::get_offsets(buffer).unwrap();
+    let events = super::get_offsets(buffer, firstbyte, lastbyte).unwrap();
     for (i, event) in events.iter().enumerate() {
         let info = lua.create_table().unwrap();
         info.set("group", event.group.as_str()).unwrap();
diff --git a/src/python.rs b/src/python.rs
index 5d42f51..77f4a6d 100644
--- a/src/python.rs
+++ b/src/python.rs
@@ -8,8 +8,13 @@ fn to_html(_py: Python, buffer: String) -> PyResult<String> {
 }
 
 #[pyfunction]
-fn get_offsets(_py: Python, buffer: String) -> PyResult<&PyDict> {
-    let events = super::get_offsets(buffer).unwrap();
+fn get_offsets(
+    _py: Python,
+    buffer: String,
+    firstbyte: usize,
+    lastbyte: usize,
+) -> PyResult<&PyDict> {
+    let events = super::get_offsets(buffer, firstbyte, lastbyte).unwrap();
     let pyevents = PyDict::new(_py);
     let mut i: u32 = 1;
     for event in events.iter() {