5 files changed, 22 insertions, 2 deletions
diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index e8192e008d..01f41184cd 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,5 +1,10 @@
 ## Rails 3.2.9 (unreleased)
 
+*   Allow store to work with an empty column.
+    Fix #4840.
+
+    *Jeremy Walker*
+
 *   Remove prepared statement from system query in postgresql adapter.
     Fix #5872.
 
diff --git a/activerecord/lib/active_record/store.rb b/activerecord/lib/active_record/store.rb
index 8cc84f81d0..49d01de365 100644
--- a/activerecord/lib/active_record/store.rb
+++ b/activerecord/lib/active_record/store.rb
@@ -36,11 +36,13 @@ module ActiveRecord
       def store_accessor(store_attribute, *keys)
         Array(keys).flatten.each do |key|
           define_method("#{key}=") do |value|
+            send("#{store_attribute}=", {}) unless send(store_attribute).is_a?(Hash)
             send(store_attribute)[key] = value
             send("#{store_attribute}_will_change!")
           end
     
           define_method(key) do
+            send("#{store_attribute}=", {}) unless send(store_attribute).is_a?(Hash)
             send(store_attribute)[key]
           end
         end
diff --git a/activerecord/test/cases/store_test.rb b/activerecord/test/cases/store_test.rb
index 5a3f9a9711..277fc9d676 100644
--- a/activerecord/test/cases/store_test.rb
+++ b/activerecord/test/cases/store_test.rb
@@ -4,7 +4,7 @@ require 'models/admin/user'
 
 class StoreTest < ActiveRecord::TestCase
   setup do
-    @john = Admin::User.create(:name => 'John Doe', :color => 'black')
+    @john = Admin::User.create(:name => 'John Doe', :color => 'black', :remember_login => true)
   end
 
   test "reading store attributes through accessors" do
@@ -31,4 +31,13 @@ class StoreTest < ActiveRecord::TestCase
     @john.color = 'red'
     assert @john.settings_changed?
   end
+
+  test "object initialization with not nullable column" do
+    assert_equal true, @john.remember_login
+  end
+
+  test "writing with not nullable column" do
+    @john.remember_login = false
+    assert_equal false, @john.remember_login
+  end
 end
diff --git a/activerecord/test/models/admin/user.rb b/activerecord/test/models/admin/user.rb
index c12c88e195..d0e628bd50 100644
--- a/activerecord/test/models/admin/user.rb
+++ b/activerecord/test/models/admin/user.rb
@@ -1,4 +1,5 @@
 class Admin::User < ActiveRecord::Base
   belongs_to :account
   store :settings, :accessors => [ :color, :homepage ]
+  store :preferences, :accessors => [ :remember_login ]
 end
diff --git a/activerecord/test/schema/schema.rb b/activerecord/test/schema/schema.rb
index d6eed1552f..2b7ea0ce34 100644
--- a/activerecord/test/schema/schema.rb
+++ b/activerecord/test/schema/schema.rb
@@ -37,7 +37,10 @@ ActiveRecord::Schema.define do
 
   create_table :admin_users, :force => true do |t|
     t.string :name
-    t.text :settings
+    t.string :settings, :null => true, :limit => 1024
+    # MySQL does not allow default values for blobs. Fake it out with a
+    # big varchar below.
+    t.string :preferences, :null => true, :default => '', :limit => 1024
     t.references :account
   end