diff --git a/astro/kosmorro/Makefile b/astro/kosmorro/Makefile
index d18779eab8a4..9a0e6e39edfb 100644
--- a/astro/kosmorro/Makefile
+++ b/astro/kosmorro/Makefile
@@ -12,7 +12,6 @@ COMMENT=	Ephemerides computation
 LICENSE=	AGPLv3
 
 BUILD_DEPENDS=	${PYNUMPY}	\
-		ronn:textproc/rubygem-ronn	\
 		${PYTHON_PKGNAMEPREFIX}skyfield>0:astro/py-skyfield@${PY_FLAVOR}\
 		${PYTHON_PKGNAMEPREFIX}dateutil>0:devel/py-dateutil@${PY_FLAVOR}\
 		${PYTHON_PKGNAMEPREFIX}tabulate>0:devel/py-tabulate@${PY_FLAVOR}\
@@ -29,7 +28,7 @@ TEST_DEPENDS=	${PYTHON_PKGNAMEPREFIX}pipenv>0:devel/py-pipenv@${PY_FLAVOR}	\
 USE_GITHUB=	yes
 
 USES=		python:3.7+ shebangfix
-USE_PYTHON=	distutils
+USE_PYTHON=	distutils noflavors
 SHEBANG_FILES=	${PORTNAME}
 
 OPTIONS_DEFINE=	PDF
@@ -39,14 +38,28 @@ PDF_RUN_DEPENDS=pdflatex:print/tex-formats
 
 NO_ARCH=	yes
 
+.include <bsd.port.pre.mk>
+
+# ronn is broken on 11.x => do not build manpages
+.if ${OSVERSION} < 1200000
+PLIST_SUB+=	MAN="@comment "
+.else
+BUILD_DEPENDS+=	ronn:textproc/rubygem-ronn
+PLIST_SUB+=	MAN=""
+.endif
+
 pre-configure:
 	${REINPLACE_CMD} -e 's|python3|${PYTHON_CMD}|' ${WRKSRC}/Makefile
+.if ${OSVERSION} < 1200000
+	${REINPLACE_CMD} -e 's|i18n manpages|manpages|' ${WRKSRC}/Makefile
+.else
 
 post-build:
 	(cd ${WRKSRC} && LC_ALL=C.UTF-8 ${MAKE} manpages)
+.endif
 
 do-test: install
 	#(cd ${WRKSRC} && ${MAKE} test)
 	${DO_NADA} # It uses unittest-data-provider which is deprecated
 
-.include <bsd.port.mk>
+.include <bsd.port.post.mk>
diff --git a/astro/kosmorro/pkg-plist b/astro/kosmorro/pkg-plist
index 91925343dbcc..0b767fc388dd 100644
--- a/astro/kosmorro/pkg-plist
+++ b/astro/kosmorro/pkg-plist
@@ -88,5 +88,5 @@ bin/kosmorro
 %%PYTHON_SITELIBDIR%%/test/ephemerides.py
 %%PYTHON_SITELIBDIR%%/test/events.py
 %%PYTHON_SITELIBDIR%%/test/testutils.py
-man/man1/kosmorro.1.gz
-man/man7/kosmorro.7.gz
+%%MAN%%man/man1/kosmorro.1.gz
+%%MAN%%man/man7/kosmorro.7.gz