diff --git a/Doc/tools/extensions/peg_highlight.py b/Doc/tools/extensions/peg_highlight.py
index f02515d3919cf2..8bc24670fbe0ab 100644
--- a/Doc/tools/extensions/peg_highlight.py
+++ b/Doc/tools/extensions/peg_highlight.py
@@ -59,7 +59,7 @@ class PEGLexer(RegexLexer):
             include("variables"),
             (r"\b(?!(NULL|EXTRA))([A-Z_]+)\b\s*(?!\()", Text,),
             (
-                r"^\s*" + _name + "\s*" + "(\[.*\])?" + "\s*" + "(\(.+\))?" + "\s*(:)",
+                r"^\s*" + _name + r"\s*" + r"(\[.*\])?" + r"\s*" + r"(\(.+\))?" + r"\s*(:)",
                 bygroups(Name.Function, None, None, Punctuation),
             ),
             (_name, Name.Function),