diff --git a/IPython/html/static/notebook/js/codemirror-ipython.js b/IPython/html/static/notebook/js/codemirror-ipython.js
index 1fb01ee3b..d01abe9e8 100644
--- a/IPython/html/static/notebook/js/codemirror-ipython.js
+++ b/IPython/html/static/notebook/js/codemirror-ipython.js
@@ -15,6 +15,11 @@ CodeMirror.requireMode('python',function(){
         }
         pythonConf.name = 'python';
         pythonConf.singleOperators = new RegExp("^[\\+\\-\\*/%&|\\^~<>!\\?]");
+        if (pythonConf.version === 3) {
+            pythonConf.identifiers = new RegExp("^[_A-Za-z\u00A1-\uFFFF][_A-Za-z0-9\u00A1-\uFFFF]*");
+        } else if (pythonConf.version === 2) {
+            pythonConf.identifiers = new RegExp("^[_A-Za-z][_A-Za-z0-9]*");
+        }
         return CodeMirror.getMode(conf, pythonConf);
     }, 'python');