diff --git a/runtime/indent/rnoweb.vim b/runtime/indent/rnoweb.vim
index 8c11e85..7396686 100644
--- a/runtime/indent/rnoweb.vim
+++ b/runtime/indent/rnoweb.vim
@@ -21,7 +21,7 @@
   let s:TeXIndent = function(substitute(&indentexpr, "()", "", ""))
 endif
 
-unlet b:did_indent
+unlet! b:did_indent
 runtime indent/r.vim
 let s:RIndent = function(substitute(&indentexpr, "()", "", ""))
 let b:did_indent = 1