diff --git a/waflib/Tools/cs.py b/waflib/Tools/cs.py
index 4a615d80..f3827f69 100644
--- a/waflib/Tools/cs.py
+++ b/waflib/Tools/cs.py
@@ -48,6 +48,7 @@ def apply_cs(self):
 	self.cs_task = tsk = self.create_task('mcs', cs_nodes, self.path.find_or_declare(self.gen))
 	tsk.env.CSTYPE = '/target:%s' % bintype
 	tsk.env.OUT    = '/out:%s' % tsk.outputs[0].abspath()
+        tsk.env.append_value('CSFLAGS', '/platform:%s' % getattr(self, 'platform', 'anycpu'))
 
 	inst_to = getattr(self, 'install_path', bintype=='exe' and '${BINDIR}' or '${LIBDIR}')
 	if inst_to: