diff --git a/runtime/doc/syntax.txt b/runtime/doc/syntax.txt
index 2fb320e..9b20478 100644
--- a/runtime/doc/syntax.txt
+++ b/runtime/doc/syntax.txt
@@ -1062,6 +1062,7 @@
 *c_no_cformat*		don't highlight %-formats in strings
 *c_no_c99*		don't highlight C99 standard items
 *c_no_c11*		don't highlight C11 standard items
+*c_no_c23*		don't highlight C23 standard items
 *c_no_bsd*		don't highlight BSD specific types
 *c_functions*		highlight function calls and definitions
 *c_function_pointers*	highlight function pointers definitions
diff --git a/runtime/doc/tags b/runtime/doc/tags
index 6d1bf96..0e4c14c 100644
--- a/runtime/doc/tags
+++ b/runtime/doc/tags
@@ -6360,6 +6360,7 @@
 c_no_bracket_error	syntax.txt	/*c_no_bracket_error*
 c_no_bsd	syntax.txt	/*c_no_bsd*
 c_no_c11	syntax.txt	/*c_no_c11*
+c_no_c23	syntax.txt	/*c_no_c23*
 c_no_c99	syntax.txt	/*c_no_c99*
 c_no_cformat	syntax.txt	/*c_no_cformat*
 c_no_curly_error	syntax.txt	/*c_no_curly_error*