diff --git a/activerecord/lib/active_record/connection_adapters/abstract/query_cache.rb b/activerecord/lib/active_record/connection_adapters/abstract/query_cache.rb
index e53ba4e66667234c78731f0bbb9e0e58aac08b03..33695c0537ff6778a28732a593e235052e2ea53f 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/query_cache.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/query_cache.rb
@@ -123,6 +123,7 @@ def cache_sql(sql, name, binds)
         # If arel is locked this is a SELECT ... FOR UPDATE or somesuch. Such
         # queries should not be cached.
         def locked?(arel)
+          arel = arel.arel if arel.is_a?(Relation)
           arel.respond_to?(:locked) && arel.locked
         end
 
diff --git a/activerecord/lib/active_record/relation.rb b/activerecord/lib/active_record/relation.rb
index 7a8f9abb36cb351465b9ee89b8c95b0623c45664..133c1a6318997a42f06ee86041232d2f03d3fdee 100644
--- a/activerecord/lib/active_record/relation.rb
+++ b/activerecord/lib/active_record/relation.rb
@@ -18,7 +18,7 @@ class Relation
     attr_reader :table, :klass, :loaded, :predicate_builder
     alias :model :klass
     alias :loaded? :loaded
-    alias :locked? :locked
+    alias :locked? :lock_value
 
     def initialize(klass, table, predicate_builder, values = {})
       @klass  = klass
diff --git a/activerecord/lib/active_record/relation/calculations.rb b/activerecord/lib/active_record/relation/calculations.rb
index c562f214c913ea1680e236a9f6b78163841e07ee..24b8be02424f8d9905bab21b1dc8f293644c5ef0 100644
--- a/activerecord/lib/active_record/relation/calculations.rb
+++ b/activerecord/lib/active_record/relation/calculations.rb
@@ -311,7 +311,7 @@ def execute_grouped_calculation(operation, column_name, distinct) #:nodoc:
         relation.group_values  = group_fields
         relation.select_values = select_values
 
-        calculated_data = @klass.connection.select_all(relation, nil, relation.bound_attributes)
+        calculated_data = @klass.connection.select_all(relation.arel, nil, relation.bound_attributes)
 
         if association
           key_ids     = calculated_data.collect { |row| row[group_aliases.first] }
diff --git a/activerecord/lib/active_record/relation/delegation.rb b/activerecord/lib/active_record/relation/delegation.rb
index dada0fddf81b4841eedcaf70f06c005242494668..8b4dd256897a9ac006c97218f6b69502e02fdaeb 100644
--- a/activerecord/lib/active_record/relation/delegation.rb
+++ b/activerecord/lib/active_record/relation/delegation.rb
@@ -44,8 +44,6 @@ def inherited(child_class)
     delegate :table_name, :quoted_table_name, :primary_key, :quoted_primary_key,
              :connection, :columns_hash, to: :klass
 
-    delegate :ast, :locked, to: :arel
-
     module ClassSpecificRelation # :nodoc:
       extend ActiveSupport::Concern
 
diff --git a/activerecord/lib/active_record/relation/finder_methods.rb b/activerecord/lib/active_record/relation/finder_methods.rb
index 5ec2dfcfc9b29d59842160b23c0c06d9529dbf2b..df8909379f8a3c7a2129f1a626e149e94b24207e 100644
--- a/activerecord/lib/active_record/relation/finder_methods.rb
+++ b/activerecord/lib/active_record/relation/finder_methods.rb
@@ -315,7 +315,7 @@ def exists?(conditions = :none)
 
       relation = construct_relation_for_exists(relation, conditions)
 
-      connection.select_value(relation, "#{name} Exists", relation.bound_attributes) ? true : false
+      connection.select_value(relation.arel, "#{name} Exists", relation.bound_attributes) ? true : false
     rescue ::RangeError
       false
     end
@@ -376,8 +376,7 @@ def find_with_associations
           if ActiveRecord::NullRelation === relation
             []
           else
-            arel = relation.arel
-            rows = connection.select_all(arel, "SQL", relation.bound_attributes)
+            rows = connection.select_all(relation.arel, "SQL", relation.bound_attributes)
             join_dependency.instantiate(rows, aliases)
           end
         end
@@ -424,9 +423,8 @@ def limited_ids_for(relation)
           "#{quoted_table_name}.#{quoted_primary_key}", relation.order_values)
 
         relation = relation.except(:select).select(values).distinct!
-        arel = relation.arel
 
-        id_rows = @klass.connection.select_all(arel, "SQL", relation.bound_attributes)
+        id_rows = @klass.connection.select_all(relation.arel, "SQL", relation.bound_attributes)
         id_rows.map { |row| row[primary_key] }
       end
 
diff --git a/activerecord/test/cases/relations_test.rb b/activerecord/test/cases/relations_test.rb
index dc81f13fe9756795923ed15e6a40ea0ac5de708c..5767dec3156c762fad0a7e59d7922f1b7efd9b1b 100644
--- a/activerecord/test/cases/relations_test.rb
+++ b/activerecord/test/cases/relations_test.rb
@@ -2007,6 +2007,12 @@ def test_merging_keeps_lhs_binds
     assert_equal binds, merged.bound_attributes
   end
 
+  def test_locked_should_not_build_arel
+    posts = Post.locked
+    assert posts.locked?
+    assert_nothing_raised { posts.lock!(false) }
+  end
+
   def test_relation_join_method
     assert_equal "Thank you for the welcome,Thank you again for the welcome", Post.first.comments.join(",")
   end
diff --git a/activerecord/test/models/post.rb b/activerecord/test/models/post.rb
index 4c913b3b723a907182d772b2519c584e13da716a..ed64e0ee5201763186238c0fa93c94fc31851fb9 100644
--- a/activerecord/test/models/post.rb
+++ b/activerecord/test/models/post.rb
@@ -22,6 +22,7 @@ def greeting
   scope :ranked_by_comments,      -> { order("comments_count DESC") }
 
   scope :limit_by, lambda { |l| limit(l) }
+  scope :locked, -> { lock }
 
   belongs_to :author
   belongs_to :readonly_author, -> { readonly }, class_name: "Author", foreign_key: :author_id