diff --git a/lib/less/parser.js b/lib/less/parser.js
index d3c6ce66..3775b8fb 100644
--- a/lib/less/parser.js
+++ b/lib/less/parser.js
@@ -1066,7 +1066,8 @@ less.Parser = function Parser(env) {
                     }
 
                     option = option && option[1];
-
+                    if (!elements)
+                        error("Missing target selector for :extend().");
                     extend = new(tree.Extend)(new(tree.Selector)(elements), option, index);
                     if (extendList) { extendList.push(extend); } else { extendList = [ extend ]; }