diff --git a/lib/rake/application.rb b/lib/rake/application.rb
index 70efd8e3e..9ac9b2130 100644
--- a/lib/rake/application.rb
+++ b/lib/rake/application.rb
@@ -392,7 +392,7 @@ def trace(*strings) # :nodoc:
 
     def sort_options(options) # :nodoc:
       options.sort_by { |opt|
-        opt.select { |o| o =~ /^-/ }.map(&:downcase).sort.reverse
+        opt.select { |o| o.is_a?(String) && o =~ /^-/ }.map(&:downcase).sort.reverse
       }
     end
     private :sort_options