diff --git a/app/assets/stylesheets/casein/casein.scss b/app/assets/stylesheets/casein/casein.scss
index c783b75..8654456 100644
--- a/app/assets/stylesheets/casein/casein.scss
+++ b/app/assets/stylesheets/casein/casein.scss
@@ -1,4 +1,4 @@
-@import 'bootstrap-sprockets';
+@import "bootstrap/functions";
 @import 'bootstrap';
 @import 'casein-bootstrap-overrides';
 
@@ -254,4 +254,4 @@ label.control-label small {
 		width: 14%;
 	margin-bottom: 0px;
 	}
-}
\ No newline at end of file
+}
diff --git a/app/assets/stylesheets/casein/login.scss b/app/assets/stylesheets/casein/login.scss
index 511fb94..c0422dd 100755
--- a/app/assets/stylesheets/casein/login.scss
+++ b/app/assets/stylesheets/casein/login.scss
@@ -1,4 +1,4 @@
-@import "bootstrap-sprockets";
+@import "bootstrap/functions";
 @import "bootstrap";
 @import "casein-bootstrap-overrides";
 
@@ -71,4 +71,4 @@ body.casein-login {
       border-radius: 6px;
     }
   }
-}
\ No newline at end of file
+}
diff --git a/app/views/casein/admin_user_sessions/new.html.erb b/app/views/casein/admin_user_sessions/new.html.erb
index 44fbfd6..d5b28b7 100644
--- a/app/views/casein/admin_user_sessions/new.html.erb
+++ b/app/views/casein/admin_user_sessions/new.html.erb
@@ -1,7 +1,7 @@
 <%= form_for @admin_user_session, url: casein_admin_user_session_path do |f| %>
 	<% if @admin_user_session.errors.any? %>
 		<div id="error_messages" class="alert alert-danger">
-			<% @admin_user_session.errors.keys.each do |key| %>
+			<% @admin_user_session.errors.attribute_names.each do |key| %>
 				<%= (key.to_s.humanize + " ") unless key == :base %>
 				<%=  @admin_user_session.errors[key].first %>
 			<% end %>
diff --git a/casein.gemspec b/casein.gemspec
index 7c5d27e..486ed50 100644
--- a/casein.gemspec
+++ b/casein.gemspec
@@ -24,7 +24,7 @@ Gem::Specification.new do |s|
   ]
 
   s.add_dependency 'authlogic', '~> 6.1'
-  s.add_dependency 'bootstrap-sass', '~> 3.4.0'
+  s.add_dependency 'bootstrap', '~> 5.3.3'
   s.add_dependency 'jquery-rails', '>= 0'
   s.add_dependency 'sassc-rails', '>= 2.0.0'
   s.add_dependency 'scrypt', '>= 1.2.1'
diff --git a/lib/casein/engine.rb b/lib/casein/engine.rb
index a2a46bc..a7133d1 100644
--- a/lib/casein/engine.rb
+++ b/lib/casein/engine.rb
@@ -2,7 +2,7 @@
 
 require 'casein'
 require 'rails'
-require 'bootstrap-sass'
+require 'bootstrap'
 require 'jquery-rails'
 
 module Casein
diff --git a/lib/casein/version.rb b/lib/casein/version.rb
index dea3601..90a0bdb 100644
--- a/lib/casein/version.rb
+++ b/lib/casein/version.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
 module Casein
-  VERSION_HASH = { major: 5, minor: 5, patch: 1, build: 0 }
+  VERSION_HASH = { major: 5, minor: 5, patch: 3, build: 0 }
   VERSION = VERSION_HASH.values.join('.')
 end