When _extract_python (lingua 3.9) has been patched to take `firstline` param into account, line numbers are off by one.

mako/ext/linguaplugin.py

diff --git a/mako/ext/linguaplugin.py b/mako/ext/linguaplugin.py
index 0e2065e..4c72589 100644
--- a/mako/ext/linguaplugin.py
+++ b/mako/ext/linguaplugin.py
@@ -33,7 +33,7 @@
             source += compat.b(' pass')
             code = io.BytesIO(source)
         for msg in self.python_extractor(
-                self.filename, self.options, code, code_lineno):
+                self.filename, self.options, code, code_lineno - 1):
             if translator_strings:
                 msg = Message(msg.msgctxt, msg.msgid, msg.msgid_plural,
                               msg.flags,