diff --git a/lib/active_model/serializer.rb b/lib/active_model/serializer.rb
index 5de2ae24..b50cb951 100644
--- a/lib/active_model/serializer.rb
+++ b/lib/active_model/serializer.rb
@@ -341,7 +341,8 @@ module ActiveModel
           next if reflection.excluded?(self)
           next unless include_directive.key?(key)
 
-          y.yield reflection.build_association(self, instance_options, include_slice)
+          association = reflection.build_association(self, instance_options, include_slice)
+          y.yield association
         end
       end
     end
@@ -390,14 +391,12 @@ module ActiveModel
 
     # @api private
     def associations_hash(adapter_options, options, adapter_instance)
-      relationships = {}
       include_directive = options.fetch(:include_directive)
-      associations(include_directive).each do |association|
-        adapter_opts = adapter_options.merge(include_directive: include_directive[association.key])
-        relationships[association.key] ||= association.serializable_hash(adapter_opts, adapter_instance)
+      include_slice = options[:include_slice]
+      associations(include_directive, include_slice).each_with_object({}) do |association, relationships|
+        adapter_opts = adapter_options.merge(include_directive: include_directive[association.key], adapter_instance: adapter_instance)
+        relationships[association.key] = association.serializable_hash(adapter_opts, adapter_instance)
       end
-
-      relationships
     end
 
     protected
diff --git a/lib/active_model/serializer/reflection.rb b/lib/active_model/serializer/reflection.rb
index c9c965b1..d4f96390 100644
--- a/lib/active_model/serializer/reflection.rb
+++ b/lib/active_model/serializer/reflection.rb
@@ -37,13 +37,13 @@ module ActiveModel
     #  1) as 'comments' and named 'comments'.
     #  2) as 'object.comments.last(1)' and named 'last_comments'.
     #
-    #  PostSerializer._reflections #=>
-    #    # [
-    #    #   HasOneReflection.new(:author, serializer: AuthorSerializer),
-    #    #   HasManyReflection.new(:comments)
-    #    #   HasManyReflection.new(:comments, { key: :last_comments }, #<Block>)
-    #    #   HasManyReflection.new(:secret_meta_data, { if: :is_admin? })
-    #    # ]
+    #  PostSerializer._reflections # =>
+    #    # {
+    #    #   author: HasOneReflection.new(:author, serializer: AuthorSerializer),
+    #    #   comments: HasManyReflection.new(:comments)
+    #    #   last_comments: HasManyReflection.new(:comments, { key: :last_comments }, #<Block>)
+    #    #   secret_meta_data: HasManyReflection.new(:secret_meta_data, { if: :is_admin? })
+    #    # }
     #
     # So you can inspect reflections in your Adapters.
     class Reflection < Field