diff --git a/lib/rspec/sidekiq/batch.rb b/lib/rspec/sidekiq/batch.rb
index f63ffdd..1d1bb8c 100644
--- a/lib/rspec/sidekiq/batch.rb
+++ b/lib/rspec/sidekiq/batch.rb
@@ -46,9 +46,17 @@ def failures
         def join
           ::Sidekiq::Worker.drain_all
 
-          @callbacks.each do |event, callback_class, options|
+          @callbacks.each do |event, callback, options|
             if event != :success || failures == 0
-              callback_class.new.send("on_#{event}", self, options)
+              case callback
+              when Class    
+                callback.new.send("on_#{event}", self, options)
+              when String
+                klass, meth = callback.split('#')
+                klass.constantize.new.send(meth, self, options)
+              else
+                raise ArgumentError, 'Unsupported callback notation'
+              end
             end
           end
         end
diff --git a/spec/rspec/sidekiq/batch_spec.rb b/spec/rspec/sidekiq/batch_spec.rb
index b8060d8..5eafd46 100644
--- a/spec/rspec/sidekiq/batch_spec.rb
+++ b/spec/rspec/sidekiq/batch_spec.rb
@@ -58,12 +58,18 @@ class MyCallback
         def on_event(status, options); end
       end
 
+      class OtherCallback
+        def foo(status, options); end
+      end
+
       before(:each) do
         batch.on(:event, MyCallback, my_arg: 42)
+        batch.on(:event, 'OtherCallback#foo', my_arg: 23)
       end
 
       it 'executes callbacks' do
         expect_any_instance_of(MyCallback).to receive(:on_event).with(subject, { my_arg: 42 })
+        expect_any_instance_of(OtherCallback).to receive(:foo).with(subject, { my_arg: 23 })
         subject.join
       end
     end