diff --git a/mode/r/r.js b/mode/r/r.js
index c422af9a4c..6feeb11f83 100644
--- a/mode/r/r.js
+++ b/mode/r/r.js
@@ -56,7 +56,7 @@ CodeMirror.defineMode("r", function(config) {
       return "variable-3";
     } else if (ch == "." && stream.match(/.[.\d]+/)) {
       return "keyword";
-    } else if (/[\w\.]/.test(ch) && ch != "_") {
+    } else if (/[a-zA-Z\.]/.test(ch)) {
       stream.eatWhile(/[\w\.]/);
       var word = stream.current();
       if (atoms.propertyIsEnumerable(word)) return "atom";