1 files changed, 3 insertions, 2 deletions
diff --git a/actionpack/lib/action_controller/cgi_process.rb b/actionpack/lib/action_controller/cgi_process.rb
index 49c5680f3f..8d24f8dd94 100644
--- a/actionpack/lib/action_controller/cgi_process.rb
+++ b/actionpack/lib/action_controller/cgi_process.rb
@@ -153,9 +153,10 @@ module ActionController #:nodoc:
       def stale_session_check!
         yield
       rescue ArgumentError => argument_error
-        if argument_error.message =~ %r{undefined class/module ([\w:]+)}
+        if argument_error.message =~ %r{undefined class/module ([\w:]*\w)}
           begin
-            Module.const_missing($1)
+            # Note that the regexp does not allow $1 to end with a ':'
+            $1.constantize
           rescue LoadError, NameError => const_error
             raise ActionController::SessionRestoreError, <<-end_msg
 Session contains objects whose class definition isn\'t available.