diff --git a/lib/service/base.rb b/lib/service/base.rb
index bde43a0f9aa..ecf1537be65 100644
--- a/lib/service/base.rb
+++ b/lib/service/base.rb
@@ -91,21 +91,17 @@ module Service
     # @!visibility private
     module StepsHelpers
       def model(name = :model, step_name = :"fetch_#{name}", optional: false)
-        steps << ModelStep.new(name, step_name, optional: optional)
+        steps << ModelStep.new(name, step_name, optional:)
       end
 
       def params(name = :default, default_values_from: nil, &block)
         contract_class = Class.new(Service::ContractBase).tap { _1.class_eval(&block) }
         const_set("#{name.to_s.classify.sub("Default", "")}Contract", contract_class)
-        steps << ContractStep.new(
-          name,
-          class_name: contract_class,
-          default_values_from: default_values_from,
-        )
+        steps << ContractStep.new(name, class_name: contract_class, default_values_from:)
       end
 
       def policy(name = :default, class_name: nil)
-        steps << PolicyStep.new(name, class_name: class_name)
+        steps << PolicyStep.new(name, class_name:)
       end
 
       def step(name)
@@ -152,7 +148,7 @@ module Service
       def run_step
         object = class_name&.new(context)
         method = object&.method(:call) || instance.method(method_name)
-        if method.parameters.any? { _1[0] != :keyreq }
+        if !object && method.parameters.any? { _1[0] != :keyreq }
           raise "In #{type} '#{name}': default values in step implementations are not allowed. Maybe they could be defined in a params or options block?"
         end
         args = context.slice(*method.parameters.select { _1[0] == :keyreq }.map(&:last))
diff --git a/spec/lib/service_spec.rb b/spec/lib/service_spec.rb
index 18575c8876a..37c1ee5d176 100644
--- a/spec/lib/service_spec.rb
+++ b/spec/lib/service_spec.rb
@@ -38,6 +38,36 @@ RSpec.describe Service do
           expect { service_class.call }.to raise_error(/In policy 'my_policy': default values/)
         end
       end
+
+      context "when providing a class which delegates its `#call` method" do
+        before do
+          service_class.class_eval do
+            class MyPolicy < Service::PolicyBase
+              class MyStrategy
+                def call
+                end
+
+                def reason
+                end
+              end
+
+              attr_reader :strategy
+
+              delegate :call, :reason, to: :strategy
+
+              def initialize(*)
+                @strategy = MyStrategy.new
+              end
+            end
+
+            policy :my_policy, class_name: MyPolicy
+          end
+        end
+
+        it "does not raise an error" do
+          expect { service_class.call }.not_to raise_error
+        end
+      end
     end
 
     describe "Generic step" do