2 files changed, 9 insertions, 6 deletions
diff --git a/activerecord/lib/active_record/associations/collection_proxy.rb b/activerecord/lib/active_record/associations/collection_proxy.rb
index 388173c1fb..adfc71d435 100644
--- a/activerecord/lib/active_record/associations/collection_proxy.rb
+++ b/activerecord/lib/active_record/associations/collection_proxy.rb
@@ -64,9 +64,12 @@ module ActiveRecord
 
       def method_missing(method, *args, &block)
         match = DynamicFinderMatch.match(method)
-        if match && match.creator?
-          attributes = match.attribute_names
-          return send(:"find_by_#{attributes.join('_and_')}", *args) || create(Hash[attributes.zip(args)])
+        if match && match.instantiator?
+          record = send(:find_or_instantiator_by_attributes, match, match.attribute_names, *args) do |r|
+            @association.send :set_owner_attributes, r
+            @association.send :add_to_target, r
+            yield(r) if block_given?
+          end
         end
 
         if target.respond_to?(method) || (!@association.klass.respond_to?(method) && Class.respond_to?(method))
diff --git a/activerecord/lib/active_record/associations/join_dependency/join_association.rb b/activerecord/lib/active_record/associations/join_dependency/join_association.rb
index 0a666598ed..c32753782f 100644
--- a/activerecord/lib/active_record/associations/join_dependency/join_association.rb
+++ b/activerecord/lib/active_record/associations/join_dependency/join_association.rb
@@ -91,12 +91,12 @@ module ActiveRecord
 
             constraint = build_constraint(reflection, table, key, foreign_table, foreign_key)
 
-            relation.from(join(table, constraint))
-
             unless conditions[i].empty?
-              relation.where(sanitize(conditions[i], table))
+              constraint = constraint.and(sanitize(conditions[i], table))
             end
 
+            relation.from(join(table, constraint))
+
             # The current table in this iteration becomes the foreign table in the next
             foreign_table = table
           end