diff --git a/lib/jsduck/doc_ast.rb b/lib/jsduck/doc_ast.rb
index 11a9eb32cbc64d707852e741849d8b0cf19be470..87c99fb92120dce0953e04cdb4c83575755e9847 100644
--- a/lib/jsduck/doc_ast.rb
+++ b/lib/jsduck/doc_ast.rb
@@ -43,7 +43,6 @@ module JsDuck
         :tagname => :class,
         :name => detect_name(:class, doc_map),
         :doc => detect_doc(docs),
-        :extends => detect_extends(doc_map),
         :mixins => detect_list(:mixins, doc_map),
         :alternateClassNames => detect_list(:alternateClassNames, doc_map),
         :aliases => detect_aliases(doc_map),
@@ -155,10 +154,6 @@ module JsDuck
       extract(doc_map, tagname, :type) || extract(doc_map, :type, :type)
     end
 
-    def detect_extends(doc_map)
-      extract(doc_map, :extends, :extends)
-    end
-
     def detect_default(tagname, doc_map)
       extract(doc_map, tagname, :default)
     end
diff --git a/lib/jsduck/tag/extends.rb b/lib/jsduck/tag/extends.rb
index 52e124130b8f79796fb29b71c868a24a8d4e1440..1bd8d5e40a24ca9afc9157a8da110720297f7c94 100644
--- a/lib/jsduck/tag/extends.rb
+++ b/lib/jsduck/tag/extends.rb
@@ -5,6 +5,7 @@ module JsDuck::Tag
   class Extends < Tag
     def initialize
       @pattern = ["extend", "extends"]
+      @key = :extends
       @ext_define_pattern = "extend"
       @ext_define_default = {:extends => "Ext.Base"}
     end
@@ -15,6 +16,10 @@ module JsDuck::Tag
       p.maybe_ident_chain(:extends)
     end
 
+    def process_doc(tags)
+      tags[0][:extends]
+    end
+
     def parse_ext_define(cls, ast)
       cls[:extends] = JsDuck::AstUtils.make_string(ast)
     end