2 files changed, 7 insertions, 4 deletions
diff --git a/activerecord/lib/active_record/locking/optimistic.rb b/activerecord/lib/active_record/locking/optimistic.rb
index 1e37ffefc6..67b8efac66 100644
--- a/activerecord/lib/active_record/locking/optimistic.rb
+++ b/activerecord/lib/active_record/locking/optimistic.rb
@@ -184,9 +184,12 @@ module ActiveRecord
       end
     end
 
+
+    # In de/serialize we change `nil` to 0, so that we can allow passing
+    # `nil` values to `lock_version`, and not result in `ActiveRecord::StaleObjectError`
+    # during update record.
     class LockingType < DelegateClass(Type::Value) # :nodoc:
       def deserialize(value)
-        # `nil` *should* be changed to 0
         super.to_i
       end
 
diff --git a/activerecord/lib/active_record/migration.rb b/activerecord/lib/active_record/migration.rb
index f30861b4d0..81fe053fe1 100644
--- a/activerecord/lib/active_record/migration.rb
+++ b/activerecord/lib/active_record/migration.rb
@@ -166,13 +166,13 @@ module ActiveRecord
   class EnvironmentMismatchError < ActiveRecordError
     def initialize(current: nil, stored: nil)
       msg =  "You are attempting to modify a database that was last run in `#{ stored }` environment.\n"
-      msg << "You are running in `#{ current }` environment."
+      msg << "You are running in `#{ current }` environment. "
       msg << "If you are sure you want to continue, first set the environment using:\n\n"
       msg << "\tbin/rails db:environment:set"
       if defined?(Rails.env)
-        super("#{msg} RAILS_ENV=#{::Rails.env}")
+        super("#{msg} RAILS_ENV=#{::Rails.env}\n\n")
       else
-        super(msg)
+        super("#{msg}\n\n")
       end
     end
   end