diff --git a/demo/c++/SConscript b/demo/c++/SConscript
index 7e04fc86a..21ff9cce3 100644
--- a/demo/c++/SConscript
+++ b/demo/c++/SConscript
@@ -19,6 +19,8 @@
 #
 # $Id$
 
+from copy import copy
+
 Import ('env')
 
 prefix = env['PREFIX']
@@ -34,7 +36,7 @@ demo_env = env.Clone()
 
 headers = env['CPPPATH'] 
 
-libraries =  env['LIBMAPNIK_LIBS']
+libraries =  copy(env['LIBMAPNIK_LIBS'])
 boost_program_options = 'boost_program_options%s' % env['BOOST_APPEND']
 libraries.extend([boost_program_options,'mapnik2'])