diff --git a/Doc/tools/sgmlconv/latex2esis.py b/Doc/tools/sgmlconv/latex2esis.py
index 74e1dc7e12f..e694f5604da 100755
--- a/Doc/tools/sgmlconv/latex2esis.py
+++ b/Doc/tools/sgmlconv/latex2esis.py
@@ -56,7 +56,7 @@ def __init__(self, found, stack):
 _begin_macro_rx = re.compile(r"[\\]([a-zA-Z]+[*]?) ?({|\s*\n?)")
 _comment_rx = re.compile("%+ ?(.*)\n[ \t]*")
 _text_rx = re.compile(r"[^]~%\\{}]+")
-_optional_rx = re.compile(r"\s*[[]([^]]*)[]]")
+_optional_rx = re.compile(r"\s*[[]([^]]*)[]]", re.MULTILINE)
 # _parameter_rx is this complicated to allow {...} inside a parameter;
 # this is useful to match tabular layout specifications like {c|p{24pt}}
 _parameter_rx = re.compile("[ \n]*{(([^{}}]|{[^}]*})*)}")