diff --git a/devel/py-marrow.mailer/Makefile b/devel/py-marrow.mailer/Makefile
index 2534efe751ac..7d9659644ec8 100644
--- a/devel/py-marrow.mailer/Makefile
+++ b/devel/py-marrow.mailer/Makefile
@@ -1,21 +1,22 @@
 PORTNAME=	marrow.mailer
 PORTVERSION=	4.0.3
+PORTREVISION=	1
 CATEGORIES=	devel python
 MASTER_SITES=	CHEESESHOP
 PKGNAMEPREFIX=	${PYTHON_PKGNAMEPREFIX}
 
 MAINTAINER=	dbaio@FreeBSD.org
 COMMENT=	Python library to ease sending emails
 WWW=		https://github.com/marrow/mailer
 
 LICENSE=	MIT
 
 RUN_DEPENDS=	${PYTHON_PKGNAMEPREFIX}marrow.util>=1.2.3:devel/py-marrow.util@${PY_FLAVOR} \
 		${PYTHON_PKGNAMEPREFIX}requests>=0:www/py-requests@${PY_FLAVOR}
 
 USES=		python:3.6+
 USE_PYTHON=	autoplist concurrent distutils
 
 NO_ARCH=	yes
 
 .include <bsd.port.mk>
diff --git a/devel/py-marrow.mailer/files/patch-marrow_mailer_message.py b/devel/py-marrow.mailer/files/patch-marrow_mailer_message.py
new file mode 100644
index 000000000000..64d50b234ad6
--- /dev/null
+++ b/devel/py-marrow.mailer/files/patch-marrow_mailer_message.py
@@ -0,0 +1,13 @@
+# base64.encodestring()
+# Deprecated alias of encodebytes(), removed in Python 3.9
+--- marrow/mailer/message.py.orig	2019-09-16 00:05:09 UTC
++++ marrow/mailer/message.py
+@@ -305,7 +305,7 @@ class Message(object):
+ 		else:
+ 			raise TypeError("Unable to read attachment contents")
+ 		
+-		part.set_payload(base64.encodestring(value))
++		part.set_payload(base64.encodebytes(value))
+ 
+ 		if not filename:
+ 			filename = name