diff --git a/Mk/bsd.gecko.mk b/Mk/bsd.gecko.mk
index c3a2372..b10ca43 100644
--- a/Mk/bsd.gecko.mk
+++ b/Mk/bsd.gecko.mk
@@ -368,6 +368,23 @@ MOZ_OPTIONS+=	--enable-pulseaudio
 MOZ_OPTIONS+=	--disable-pulseaudio
 .endif
 
+.if ${PORT_OPTIONS:MSNDIO}
+LIB_DEPENDS+=	libsndio.so:audio/sndio
+# In mail/thunderbird and www/seamonky media/libcubeb is in
+# ${WRKSRC}/mozilla instead of ${WRKSRC}.  All other gecko-based ports
+# have it in ${WRKSRC}.
+MOZ_SRC?=	${WRKSRC}
+post-patch-SNDIO-on:
+	@${REINPLACE_CMD} -e 's|OpenBSD|${OPSYS}|g' \
+		${MOZ_SRC}/media/libcubeb/src/moz.build \
+		${MOZ_SRC}/media/libcubeb/tests/moz.build \
+		${MOZ_SRC}/toolkit/library/moz.build
+	@${REINPLACE_CMD} -e 's|OS==\"openbsd\"|OS==\"${OPSYS:tl}\"|g' \
+		${MOZ_SRC}/media/webrtc/trunk/webrtc/build/common.gypi
+	@${ECHO} "OS_LIBS += ['sndio']" >> \
+		${MOZ_SRC}/media/webrtc/signaling/test/common.build
+.endif
+
 .if ${PORT_OPTIONS:MRUST}
 BUILD_DEPENDS+=	rustc:${RUST_PORT}
 RUST_PORT?=		lang/rust
diff --git a/mail/thunderbird/Makefile b/mail/thunderbird/Makefile
index 8fb0534..517354b 100644
--- a/mail/thunderbird/Makefile
+++ b/mail/thunderbird/Makefile
@@ -47,6 +47,7 @@ MOZ_OPTIONS=	--program-transform-name='s/thunderbird/${MOZILLA}/' \
 MOZ_MK_OPTIONS=	MOZ_THUNDERBIRD=1 MAIL_PKG_SHARED=1
 MOZ_EXPORT=		MOZ_THUNDERBIRD=1 MAIL_PKG_SHARED=1
 MOZ_PKGCONFIG_FILES=
+MOZ_SRC=	${WRKSRC}/mozilla
 
 PORTNAME_ICON=	${MOZILLA}.png
 PORTNAME_ICON_SRC=	${PREFIX}/lib/${MOZILLA}/chrome/icons/default/default48.png
diff --git a/www/firefox/Makefile.options b/www/firefox/Makefile.options
index 994512a..1da3840 100644
--- a/www/firefox/Makefile.options
+++ b/www/firefox/Makefile.options
@@ -5,11 +5,11 @@ OPTIONS_DEFINE+= 	BUNDLED_CAIRO CANBERRA DBUS DEBUG DTRACE FFMPEG GCONF \
 			OPTIMIZED_CFLAGS PGO PROFILE TEST
 
 OPTIONS_DEFAULT+=	DBUS DTRACE FFMPEG OPTIMIZED_CFLAGS \
-			${OPTIONS_MULTI_AUDIO} \
+			ALSA PULSEAUDIO \
 			${MACHINE_CPU:tu:MSOFTFP:S/SOFTFP/INTEGER_SAMPLES/}
 
 OPTIONS_MULTI+=		AUDIO
-OPTIONS_MULTI_AUDIO=	ALSA PULSEAUDIO
+OPTIONS_MULTI_AUDIO=	ALSA PULSEAUDIO SNDIO
 
 # dragonfly, sparc64, riscv
 .if !exists(/usr/sbin/dtrace)
diff --git a/www/seamonkey/Makefile b/www/seamonkey/Makefile
index 5e0f6c7..925a950 100644
--- a/www/seamonkey/Makefile
+++ b/www/seamonkey/Makefile
@@ -47,6 +47,7 @@ MOZ_OPTIONS+=	--program-transform-name='s/seamonkey/${MOZILLA}/' \
 
 USE_MOZILLA=	# empty
 MOZ_PKGCONFIG_FILES=
+MOZ_SRC=	${WRKSRC}/mozilla
 
 NOT_FOR_ARCHS=	ia64
 
@@ -60,6 +61,8 @@ COMPOSER_DESC?=	HTML Composer module
 LDAP_DESC?=	LDAP support for Mailnews
 MAILNEWS_DESC?=	Mail and News modules
 
+SNDIO_BROKEN=	missing sndio support
+
 .include "${.CURDIR}/../../www/firefox/Makefile.options"
 .include <bsd.port.options.mk>