diff --git a/activerecord/CHANGELOG b/activerecord/CHANGELOG
index f0bf07e65b1afd1bf37b5d08cdf9bbd40c7e598b..90885b18c0ab792b08d6cd62d9d1d8eb32b26d2b 100644
--- a/activerecord/CHANGELOG
+++ b/activerecord/CHANGELOG
@@ -1,5 +1,7 @@
 *SVN*
 
+* Ensure optimistic locking handles nil #lock_version values properly.  Closes #10510 [rick]
+
 * Make the Fixtures Test::Unit enhancements more supporting for double-loaded test cases.  Closes #10379 [brynary]
 
 * Fix that validates_acceptance_of still works for non-existent tables (useful for bootstrapping new databases).  Closes #10474 [hasmanyjosh]
diff --git a/activerecord/lib/active_record/locking/optimistic.rb b/activerecord/lib/active_record/locking/optimistic.rb
index ecd6a2b258cb5ec671f64cc06793b6385ecf89ef..799309c17b1c7fdd746616d54dcae2b0cd1f21e9 100644
--- a/activerecord/lib/active_record/locking/optimistic.rb
+++ b/activerecord/lib/active_record/locking/optimistic.rb
@@ -70,7 +70,7 @@ def update_with_lock #:nodoc:
           return update_without_lock unless locking_enabled?
 
           lock_col = self.class.locking_column
-          previous_value = send(lock_col)
+          previous_value = send(lock_col).to_i
           send(lock_col + '=', previous_value + 1)
 
           begin
diff --git a/activerecord/test/locking_test.rb b/activerecord/test/locking_test.rb
index 97fbfaaeb18921f661669b5ec94bdb8acb522c09..9a3b76e810cefb43d94f307005232055bd865276 100644
--- a/activerecord/test/locking_test.rb
+++ b/activerecord/test/locking_test.rb
@@ -64,6 +64,15 @@ def test_lock_new
 
     assert_raises(ActiveRecord::StaleObjectError) { p2.save! }
   end
+  
+  def test_lock_new_with_nil
+    p1 = Person.new(:first_name => 'anika')
+    p1.save!
+    p1.lock_version = nil # simulate bad fixture or column with no default
+    p1.save!
+    assert_equal 1, p1.lock_version
+  end
+    
 
   def test_lock_column_name_existing
     t1 = LegacyThing.find(1)