diff --git a/lib/jekyll/deprecator.rb b/lib/jekyll/deprecator.rb
index 88e959b7..ae074f33 100644
--- a/lib/jekyll/deprecator.rb
+++ b/lib/jekyll/deprecator.rb
@@ -1,6 +1,7 @@
 module Jekyll
   class Deprecator
     def self.process(args)
+      no_subcommand(args)
       deprecation_message args, "--server", "The --server command has been replaced by the \
                           'serve' subcommand."
       deprecation_message args, "--no-server", "To build Jekyll without launching a server, \
@@ -15,6 +16,14 @@ module Jekyll
       deprecation_message args, "--url", "The 'url' setting can only be set in your config files."
     end
 
+    def self.no_subcommand(args)
+      if args.size == 0 || args.first =~ /^--/
+        Jekyll::Logger.error "Deprecation:", "Jekyll now uses subcommands instead of just \
+                            switches. Run `jekyll help' to find out more."
+        exit(1)
+      end
+    end
+
     def self.deprecation_message(args, deprecated_argument, message)
       if args.include?(deprecated_argument)
         Jekyll::Logger.error "Deprecation:", message