diff --git a/lib/faraday/options.rb b/lib/faraday/options.rb
index bbb913d51..8e8af499d 100644
--- a/lib/faraday/options.rb
+++ b/lib/faraday/options.rb
@@ -171,8 +171,12 @@ def self.attribute_options
       @attribute_options ||= {}
     end
 
-    def self.memoized(key)
-      memoized_attributes[key.to_sym] = Proc.new
+    def self.memoized(key, &block)
+      unless block_given?
+        raise ArgumentError, '#memoized must be called with a block'
+      end
+
+      memoized_attributes[key.to_sym] = block
       class_eval <<-RUBY, __FILE__, __LINE__ + 1
         def #{key}() self[:#{key}]; end
       RUBY
diff --git a/spec/faraday/options/options_spec.rb b/spec/faraday/options/options_spec.rb
index a9d73199b..9758eccf5 100644
--- a/spec/faraday/options/options_spec.rb
+++ b/spec/faraday/options/options_spec.rb
@@ -250,6 +250,18 @@ class ParentOptions < Faraday::Options.new(:a, :b, :c)
       end
     end
 
+    describe '#memoized' do
+      subject(:options_class) { Class.new(ParentOptions) }
+      it 'requires block' do
+        expect { options_class.memoized(:a) }.to raise_error(ArgumentError)
+      end
+
+      it 'accepts block' do
+        options_class.memoized(:a) { :foo }
+        expect(options_class.new.a).to eql(:foo)
+      end
+    end
+
     describe '#fetch' do
       subject { SubOptions.new }