diff --git a/doc/manual.html b/doc/manual.html
index 119c5a0cea55860840bab1637398f8113aedadfa..ad6a010158c584562e3dd598a5d1cd44c6ef0de9 100644
--- a/doc/manual.html
+++ b/doc/manual.html
@@ -298,6 +298,14 @@
       generate events that allow CodeMirror to properly detect it.
       Thus, it polls. Default is 100 milliseconds.</dd>
 
+      <dt id="option_flattenSpans"><code>flattenSpans (boolean)</code></dt>
+      <dd>By default, CodeMirror will combine adjacent tokens into a
+      single span if they have the same class. This will result in a
+      simpler DOM tree, and thus perform better. With some kinds of
+      styling (such as rounded corners), this will change the way the
+      document looks. You can set this option to false to disable this
+      behavior.</dd>
+
       <dt id="option_viewportMargin"><code>viewportMargin (integer)</code></dt>
       <dd>Specifies the amount of lines that are rendered above and
       below the part of the document that's currently scrolled into
diff --git a/lib/codemirror.js b/lib/codemirror.js
index 9105f484a0be5004ff45ba9cf5a337e51f8b7989..86197130be61bab474e9b4a80af84297ec339c32 100644
--- a/lib/codemirror.js
+++ b/lib/codemirror.js
@@ -2539,6 +2539,7 @@ window.CodeMirror = (function() {
     cursorHeight: 1,
     workTime: 100,
     workDelay: 200,
+    flattenSpans: true,
     pollInterval: 100,
     undoDepth: 40,
     viewportMargin: 100,
@@ -3085,14 +3086,14 @@ window.CodeMirror = (function() {
   // array, which contains alternating fragments of text and CSS
   // classes.
   function highlightLine(cm, line, state) {
-    var mode = cm.view.mode;
+    var mode = cm.view.mode, flattenSpans = cm.options.flattenSpans;
     var stream = new StringStream(line.text, cm.options.tabSize), st = line.styles || (line.styles = []);
     var pos = st.length = 0;
     if (line.text == "" && mode.blankLine) mode.blankLine(state);
     while (!stream.eol()) {
       var style = mode.token(stream, state), substr = stream.current();
       stream.start = stream.pos;
-      if (pos && st[pos-1] == style) {
+      if (flattenSpans && pos && st[pos-1] == style) {
         st[pos-2] += substr;
       } else if (substr) {
         st[pos++] = substr; st[pos++] = style;