diff --git a/lib/shoulda/matchers/active_record/association_matchers/model_reflection.rb b/lib/shoulda/matchers/active_record/association_matchers/model_reflection.rb
index 882808f42..40eb27f9d 100644
--- a/lib/shoulda/matchers/active_record/association_matchers/model_reflection.rb
+++ b/lib/shoulda/matchers/active_record/association_matchers/model_reflection.rb
@@ -35,12 +35,12 @@ def join_table_name
             join_table_name.to_s
           end
 
-          def association_relation
+          def association_relation(related_instance)
             relation = associated_class.all
 
             if reflection.scope
               # Source: AR::Associations::AssociationScope#eval_scope
-              relation.instance_exec(subject, &reflection.scope)
+              relation.instance_exec(related_instance, &reflection.scope)
             else
               relation
             end
diff --git a/lib/shoulda/matchers/active_record/association_matchers/model_reflector.rb b/lib/shoulda/matchers/active_record/association_matchers/model_reflector.rb
index 0d0503c9b..e54bb1e4c 100644
--- a/lib/shoulda/matchers/active_record/association_matchers/model_reflector.rb
+++ b/lib/shoulda/matchers/active_record/association_matchers/model_reflector.rb
@@ -5,7 +5,7 @@ module AssociationMatchers
         # @private
         class ModelReflector
           delegate :associated_class, :through?, :join_table_name,
-            :association_relation, :polymorphic?, :foreign_key,
+            :polymorphic?, :foreign_key,
             :association_foreign_key, to: :reflection
 
           def initialize(subject, name)
@@ -13,6 +13,10 @@ def initialize(subject, name)
             @name = name
           end
 
+          def association_relation
+            reflection.association_relation(subject)
+          end
+
           def reflection
             @reflection ||= reflect_on_association(name)
           end
diff --git a/spec/unit/shoulda/matchers/active_record/association_matchers/model_reflection_spec.rb b/spec/unit/shoulda/matchers/active_record/association_matchers/model_reflection_spec.rb
index 6be807281..d47b0894d 100644
--- a/spec/unit/shoulda/matchers/active_record/association_matchers/model_reflection_spec.rb
+++ b/spec/unit/shoulda/matchers/active_record/association_matchers/model_reflection_spec.rb
@@ -95,13 +95,29 @@
             person_model = define_model(:person, country_id: :integer) do
               belongs_to :country, -> { where(mood: 'nice') }
             end
+            person_instance = person_model.new(spirit: 'nice')
             delegate_reflection = person_model.reflect_on_association(:country)
             reflection = described_class.new(delegate_reflection)
 
-            actual_sql = reflection.association_relation.to_sql
+            actual_sql = reflection.association_relation(person_instance).to_sql
             expected_sql = Country.where(mood: 'nice').to_sql
             expect(actual_sql).to eq expected_sql
           end
+
+          it 'pass instance of association source to block' do
+            spy = spy('spy')
+            define_model(:country, mood: :string)
+            person_model = define_model(:person, country_id: :integer) do
+              belongs_to :country, ->(person) { spy.who(person) }
+            end
+            person_instance = person_model.new(spirit: 'nice')
+            delegate_reflection = person_model.reflect_on_association(:country)
+            reflection = described_class.new(delegate_reflection)
+
+            reflection.association_relation(person_instance)
+
+            expect(spy).to have_received(:who).with(person_instance)
+          end
         end
 
         context 'when the scope is nil' do
@@ -113,7 +129,7 @@
             delegate_reflection = person_model.reflect_on_association(:country)
             reflection = described_class.new(delegate_reflection)
 
-            actual_sql = reflection.association_relation.to_sql
+            actual_sql = reflection.association_relation(person_model).to_sql
             expected_sql = Country.all.to_sql
             expect(actual_sql).to eq expected_sql
           end