Index: lib/merb/server.rb
===================================================================
--- lib/merb/server.rb	(revision 1223)
+++ lib/merb/server.rb	(working copy)
@@ -71,7 +71,7 @@
         options = {}

         # Environment variables always win
-        options[:environment] = ENV['MERB_ENV']
+        options[:environment] = ENV['MERB_ENV'] if ENV['MERB_ENV']

         # Build a parser for the command line arguements
         opts = OptionParser.new do |opts|