diff --git a/activerecord/lib/active_record/relation/query_methods.rb b/activerecord/lib/active_record/relation/query_methods.rb
index a22849f4a609c..f694a901f476b 100644
--- a/activerecord/lib/active_record/relation/query_methods.rb
+++ b/activerecord/lib/active_record/relation/query_methods.rb
@@ -275,15 +275,6 @@ def group!(*args) # :nodoc:
 
     # Allows to specify an order attribute:
     #
-    #   User.order('name')
-    #   => SELECT "users".* FROM "users" ORDER BY name
-    #
-    #   User.order('name DESC')
-    #   => SELECT "users".* FROM "users" ORDER BY name DESC
-    #
-    #   User.order('name DESC, email')
-    #   => SELECT "users".* FROM "users" ORDER BY name DESC, email
-    #
     #   User.order(:name)
     #   => SELECT "users".* FROM "users" ORDER BY "users"."name" ASC
     #
@@ -292,6 +283,15 @@ def group!(*args) # :nodoc:
     #
     #   User.order(:name, email: :desc)
     #   => SELECT "users".* FROM "users" ORDER BY "users"."name" ASC, "users"."email" DESC
+    #
+    #   User.order('name')
+    #   => SELECT "users".* FROM "users" ORDER BY name
+    #
+    #   User.order('name DESC')
+    #   => SELECT "users".* FROM "users" ORDER BY name DESC
+    #
+    #   User.order('name DESC, email')
+    #   => SELECT "users".* FROM "users" ORDER BY name DESC, email
     def order(*args)
       check_if_method_has_arguments!(:order, args)
       spawn.order!(*args)
@@ -1030,13 +1030,14 @@ def build_order(arel)
       arel.order(*orders) unless orders.empty?
     end
 
-    VALID_DIRECTIONS = [:asc, :desc, 'asc', 'desc'] # :nodoc:
+    VALID_DIRECTIONS = [:asc, :desc, :ASC, :DESC,
+                        'asc', 'desc', 'ASC', 'DESC'] # :nodoc:
 
     def validate_order_args(args)
       args.grep(Hash) do |h|
-        h.values.map(&:downcase).each do |value|
-          raise ArgumentError, "Direction '#{value}' is invalid. Valid " \
-                               "directions are asc and desc." unless VALID_DIRECTIONS.include?(value)
+        h.values.each do |value|
+          raise ArgumentError, "Direction \"#{value}\" is invalid. Valid " \
+                               "directions are: #{VALID_DIRECTIONS.inspect}" unless VALID_DIRECTIONS.include?(value)
         end
       end
     end
diff --git a/activerecord/test/cases/relations_test.rb b/activerecord/test/cases/relations_test.rb
index a08171cfccf80..72b96dd3e9de7 100644
--- a/activerecord/test/cases/relations_test.rb
+++ b/activerecord/test/cases/relations_test.rb
@@ -205,31 +205,21 @@ def test_finding_with_asc_order_with_string
     assert_equal [topics(:first), topics(:second), topics(:third), topics(:fourth), topics(:fifth)], topics.to_a
   end
 
-  def test_nothing_raises_on_upcase_desc_arg
-    Topic.order(id: "DESC")
-  end
-
-  def test_nothing_raises_on_downcase_desc_arg
-    Topic.order(id: "desc")
-  end
-
-  def test_nothing_raises_on_upcase_asc_arg
-    Topic.order(id: "ASC")
-  end
-
-  def test_nothing_raises_on_downcase_asc_arg
-    Topic.order(id: "asc")
-  end
+  def test_support_upper_and_lower_case_directions
+    assert_includes Topic.order(id: "ASC").to_sql, "ASC"
+    assert_includes Topic.order(id: "asc").to_sql, "ASC"
+    assert_includes Topic.order(id: :ASC).to_sql, "ASC"
+    assert_includes Topic.order(id: :asc).to_sql, "ASC"
 
-  def test_nothing_raises_on_case_insensitive_args
-    Topic.order(id: "DeSc")
-    Topic.order(id: :DeSc)
-    Topic.order(id: "aSc")
-    Topic.order(id: :aSc)
+    assert_includes Topic.order(id: "DESC").to_sql, "DESC"
+    assert_includes Topic.order(id: "desc").to_sql, "DESC"
+    assert_includes Topic.order(id: :DESC).to_sql, "DESC"
+    assert_includes Topic.order(id: :desc).to_sql,"DESC"
   end
 
   def test_raising_exception_on_invalid_hash_params
-    assert_raise(ArgumentError) { Topic.order(:name, "id DESC", id: :asfsdf) }
+    e = assert_raise(ArgumentError) { Topic.order(:name, "id DESC", id: :asfsdf) }
+    assert_equal 'Direction "asfsdf" is invalid. Valid directions are: [:asc, :desc, :ASC, :DESC, "asc", "desc", "ASC", "DESC"]', e.message
   end
 
   def test_finding_last_with_arel_order