diff --git a/syntax/cpp.vim b/syntax/cpp.vim
index 23feecd..882c100 100644
--- a/syntax/cpp.vim
+++ b/syntax/cpp.vim
@@ -71,8 +71,9 @@ if !exists('cpp_no_cpp14')
 endif
 
 " C++17
-if !exists('cpp_no_cpp17')
+if exists('cpp_experimental') && !exists('cpp_no_cpp17')
   " Attribute Specifier Sequence
+  " FIXME: This matches range-for and switch case statements
   " Match: [[using attribute-namespace: attribute-list]]
   syn match cppAttributeUsingNamespace '\s\+\zs\w\+\ze\s*:' contained contains=cppAttributeUsing
   syn keyword cppAttributeUsing using contained
@@ -86,7 +87,7 @@ if !exists('cpp_no_cpp17')
 endif
 
 " C++20
-if !exists('cpp_no_cpp20')
+if exists('cpp_experimental') && !exists('cpp_no_cpp20')
   syn keyword cppStatement concept requires
 
   " TODO: Attribute Specifier Sequence