diff --git a/Doc/reference/lexical_analysis.rst b/Doc/reference/lexical_analysis.rst
index 6cfe2b3d4f7..65d9de5534a 100644
--- a/Doc/reference/lexical_analysis.rst
+++ b/Doc/reference/lexical_analysis.rst
@@ -720,7 +720,7 @@ for the contents of the string is:
                :   ("," `conditional_expression` | "," "*" `or_expr`)* [","]
                : | `yield_expression`
    conversion: "s" | "r" | "a"
-   format_spec: (`literal_char` | NULL | `replacement_field`)*
+   format_spec: (`literal_char` | `replacement_field`)*
    literal_char: <any code point except "{", "}" or NULL>
 
 The parts of the string outside curly braces are treated literally,