Ruby on rails devise flash messages

I'm using devise gem in my application. After logging out i redirect user to the home page. When I go to log in page again, I see "You have been logged out" message from previous session. It happens even if I refresh my home page 20 times. Here's my devise_error_messages! method's code:

def devise_error_messages!
flash_errors = []
flash_notices = []

if !flash.empty?
  flash_errors.push(flash[:error]) if flash[:error]
  flash_errors.push(flash[:alert]) if flash[:alert]
  flash_notices.push(flash[:notice]) if flash[:notice]
end

return "" if resource.errors.empty? && flash_errors.empty? && flash_notices.empty?

# not important output styling
errors = resource.errors.empty? ? flash_errors : resource.errors.full_messages
error_icon = "<span class=\"glyphicon glyphicon-exclamation-sign\" aria-hidden=\"true\">&nbsp;</span>"
errors = errors.map { |msg| "<p>" + error_icon + msg + "</p>" }.join
errors = "<div class=\"alert alert-danger\" role=\"alert\">" + errors + "</div>" unless errors.empty?

notice_icon = "<span class=\"glyphicon glyphicon-ok\" aria-hidden=\"true\">&nbsp;</span>"
notices = flash_notices.map { |msg| "<p>" + notice_icon + msg + "</p>" }.join
notices = "<div class=\"alert alert-success\" role=\"alert\">" + notices + "</div>" unless notices.empty?

html = <<-HTML
<div id="error_explanation">
  #{errors}
  #{notices}
</div>
HTML

html.html_safe
end

I'm using Rails 4.2.3, ruby 2.2.2 and devise 3.4.1. Is there any way to get rid of that old message? Any help would be appreciated. Thank you!