diff --git a/lib/active_model/serializer.rb b/lib/active_model/serializer.rb
index 8281e26e..1208ca80 100644
--- a/lib/active_model/serializer.rb
+++ b/lib/active_model/serializer.rb
@@ -70,7 +70,7 @@ module ActiveModel
         end
 
         def key
-          options[:as] || name
+          options[:key] || name
         end
       end
 
@@ -126,10 +126,10 @@ module ActiveModel
             class_eval "def #{attr}() object.#{attr} end", __FILE__, __LINE__
           end
 
-          # if :as is specified without :serializer, then use conventions
+          # if :key is specified without :serializer, then use conventions
           # to determine the serializer
-          if options[:as] && !options[:serializer]
-            options[:serializer] = const_get("#{options[:as].to_s.camelize.singularize}Serializer")
+          if options[:key] && !options[:serializer]
+            options[:serializer] = const_get("#{options[:key].to_s.camelize.singularize}Serializer")
           else
             options[:serializer] ||= const_get("#{attr.to_s.camelize}Serializer")
           end
@@ -171,10 +171,10 @@ module ActiveModel
       #
       #     { :posts => { :has_many => :posts } }
       #
-      # If :as is used:
+      # If :key is used:
       #
       #     class PostsSerializer < ActiveModel::Serializer
-      #       has_many :my_posts, :as => :posts
+      #       has_many :posts, :key => :my_posts
       #     end
       #
       # the hash looks like this:
@@ -198,7 +198,7 @@ module ActiveModel
         end
 
         associations = _associations.inject({}) do |hash, association|
-          model_association = klass.reflect_on_association(association.key)
+          model_association = klass.reflect_on_association(association.name)
           hash.merge association.key => { model_association.macro => model_association.name }
         end
 
diff --git a/test/serializer_test.rb b/test/serializer_test.rb
index 0ceed941..5fd71cdd 100644
--- a/test/serializer_test.rb
+++ b/test/serializer_test.rb
@@ -440,8 +440,8 @@ class SerializerTest < ActiveModel::TestCase
   end
 
   class CustomBlogSerializer < ActiveModel::Serializer
-    has_many :public_posts, :as => :posts, :serializer => PostSerializer
-    has_one :public_user, :as => :user, :serializer => UserSerializer
+    has_many :public_posts, :key => :posts, :serializer => PostSerializer
+    has_one :public_user, :key => :user, :serializer => UserSerializer
   end
 
   def test_associations_with_as
@@ -478,8 +478,8 @@ class SerializerTest < ActiveModel::TestCase
       const_set(:UserSerializer, UserSerializer)
       const_set(:PostSerializer, PostSerializer)
 
-      has_many :public_posts, :as => :posts
-      has_one :public_user, :as => :user
+      has_many :public_posts, :key => :posts
+      has_one :public_user, :key => :user
     end
 
     posts = [
@@ -559,8 +559,8 @@ class SerializerTest < ActiveModel::TestCase
       end
 
       attributes :name, :age
-      has_many :my_posts, :as => :posts, :serializer => Class.new
-      has_one :my_parent, :as => :parent, :serializer => Class.new
+      has_many :posts, :key => :my_posts, :serializer => Class.new
+      has_one :parent, :key => :my_parent, :serializer => Class.new
     end
 
     assert_equal serializer.schema, {