2 files changed, 5 insertions, 3 deletions
diff --git a/activerecord/test/cases/primary_keys_test.rb b/activerecord/test/cases/primary_keys_test.rb
index 1b915387be..51ddd406ed 100644
--- a/activerecord/test/cases/primary_keys_test.rb
+++ b/activerecord/test/cases/primary_keys_test.rb
@@ -180,6 +180,11 @@ class PrimaryKeysTest < ActiveRecord::TestCase
       assert !col1.equal?(col2)
     end
   end
+
+  def test_auto_detect_primary_key_from_schema
+    MixedCaseMonkey.reset_primary_key
+    assert_equal "monkeyID", MixedCaseMonkey.primary_key
+  end
 end
 
 class PrimaryKeyWithNoConnectionTest < ActiveRecord::TestCase
@@ -214,4 +219,3 @@ if current_adapter?(:MysqlAdapter, :Mysql2Adapter)
     end
   end
 end
-
diff --git a/activerecord/test/models/mixed_case_monkey.rb b/activerecord/test/models/mixed_case_monkey.rb
index 4d37371777..1c35006665 100644
--- a/activerecord/test/models/mixed_case_monkey.rb
+++ b/activerecord/test/models/mixed_case_monkey.rb
@@ -1,5 +1,3 @@
 class MixedCaseMonkey < ActiveRecord::Base
-  self.primary_key = 'monkeyID'
-
   belongs_to :man
 end