--- a/mail/config/mozconfigs/macosx64/debug
+++ b/mail/config/mozconfigs/macosx64/debug
@@ -18,8 +18,12 @@ MOZ_REQUIRE_ADDON_SIGNING=0
 # Package js shell
 export MOZ_PACKAGE_JSSHELL=1
 
 ac_add_options --with-ccache
 
 # Run client.py
 mk_add_options CLIENT_PY_ARGS="$([ -f $topsrcdir/build/client.py-args ] && cat $topsrcdir/build/client.py-args)"
 mk_add_options ALWAYS_RUN_CLIENT_PY=1
+
+# Disable stylo.
+# https://bugzilla.mozilla.org/show_bug.cgi?id=1380171
+ac_add_options --disable-stylo

--- a/mail/config/mozconfigs/macosx64/l10n-mozconfig
+++ b/mail/config/mozconfigs/macosx64/l10n-mozconfig
@@ -12,8 +12,12 @@ ac_add_options --enable-calendar
 # Disable checking that add-ons are signed by the trusted root
 MOZ_ADDON_SIGNING=0
 # Disable enforcing that add-ons are signed by the trusted root
 MOZ_REQUIRE_ADDON_SIGNING=0
 
 # Run client.py
 mk_add_options CLIENT_PY_ARGS="$([ -f $topsrcdir/build/client.py-l10n-args ] && cat $topsrcdir/build/client.py-l10n-args)"
 mk_add_options ALWAYS_RUN_CLIENT_PY=1
+
+# Disable stylo.
+# https://bugzilla.mozilla.org/show_bug.cgi?id=1380171
+ac_add_options --disable-stylo

--- a/mail/config/mozconfigs/macosx64/nightly
+++ b/mail/config/mozconfigs/macosx64/nightly
@@ -31,8 +31,12 @@ MOZ_ADDON_SIGNING=0
 # Disable enforcing that add-ons are signed by the trusted root
 MOZ_REQUIRE_ADDON_SIGNING=0
 
 ac_add_options --with-ccache
 
 # Run client.py
 mk_add_options CLIENT_PY_ARGS="$([ -f $topsrcdir/build/client.py-args ] && cat $topsrcdir/build/client.py-args)"
 mk_add_options ALWAYS_RUN_CLIENT_PY=1
+
+# Disable stylo.
+# https://bugzilla.mozilla.org/show_bug.cgi?id=1380171
+ac_add_options --disable-stylo

--- a/mail/config/mozconfigs/macosx64/release
+++ b/mail/config/mozconfigs/macosx64/release
@@ -28,8 +28,12 @@ MOZ_ADDON_SIGNING=0
 MOZ_REQUIRE_ADDON_SIGNING=0
 
 # Package js shell
 export MOZ_PACKAGE_JSSHELL=1
 
 # Run client.py
 mk_add_options CLIENT_PY_ARGS="$([ -f $topsrcdir/build/client.py-args ] && cat $topsrcdir/build/client.py-args)"
 mk_add_options ALWAYS_RUN_CLIENT_PY=1
+
+# Disable stylo.
+# https://bugzilla.mozilla.org/show_bug.cgi?id=1380171
+ac_add_options --disable-stylo