diff --git a/runtime/ftplugin/tcl.vim b/runtime/ftplugin/tcl.vim
index c5bc303..1cc24d3 100644
--- a/runtime/ftplugin/tcl.vim
+++ b/runtime/ftplugin/tcl.vim
@@ -32,5 +32,6 @@
 
 " Restore the saved compatibility options.
 let &cpo = s:cpo_save
+unlet s:cpo_save
 
 " vim: set et ts=4 sw=4 tw=78: