2 files changed, 14 insertions, 6 deletions
diff --git a/actionpack/lib/action_dispatch/middleware/session/abstract_store.rb b/actionpack/lib/action_dispatch/middleware/session/abstract_store.rb
index 45a00b5056..e82132b445 100644
--- a/actionpack/lib/action_dispatch/middleware/session/abstract_store.rb
+++ b/actionpack/lib/action_dispatch/middleware/session/abstract_store.rb
@@ -7,6 +7,15 @@ require 'active_support/core_ext/object/blank'
 module ActionDispatch
   module Session
     class SessionRestoreError < StandardError #:nodoc:
+      attr_reader :original_exception
+
+      def initialize(const_error)
+        @original_exception = const_error
+
+        super("Session contains objects whose class definition isn't available.\n" +
+          "Remember to require the classes for all objects kept in the session.\n" +
+          "(Original exception: #{const_error.message} [#{const_error.class}])\n")
+      end
     end
 
     module DestroyableSession
@@ -58,11 +67,8 @@ module ActionDispatch
           begin
             # Note that the regexp does not allow $1 to end with a ':'
             $1.constantize
-          rescue LoadError, NameError => const_error
-            raise ActionDispatch::Session::SessionRestoreError,
-              "Session contains objects whose class definition isn't available.\n" +
-              "Remember to require the classes for all objects kept in the session.\n" +
-              "(Original exception: #{const_error.message} [#{const_error.class}])\n"
+          rescue LoadError, NameError => e
+            raise ActionDispatch::Session::SessionRestoreError, e, e.backtrace
           end
           retry
         else
diff --git a/actionpack/lib/action_dispatch/middleware/templates/rescues/routing_error.erb b/actionpack/lib/action_dispatch/middleware/templates/rescues/routing_error.erb
index f06c07daa5..177d383e94 100644
--- a/actionpack/lib/action_dispatch/middleware/templates/rescues/routing_error.erb
+++ b/actionpack/lib/action_dispatch/middleware/templates/rescues/routing_error.erb
@@ -12,4 +12,6 @@
 <% end %>
 <p>
   Try running <code>rake routes</code> for more information on available routes.
-</p>
-\ No newline at end of file
+</p>
+
+<%= render :template => "rescues/_trace" %>