--- a/mail/config/mozconfigs/macosx64/debug
+++ b/mail/config/mozconfigs/macosx64/debug
@@ -13,16 +13,16 @@ export MOZ_DEBUG_SYMBOLS=1
 # 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
 
 # Package js shell
 export MOZ_PACKAGE_JSSHELL=1
 
-ac_add_options --with-ccache
+. "$topsrcdir/build/mozconfig.cache"
 
 # 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
 
 # XXX hack to work around dsymutil failing on OSX builds (bug 1380381, 1382262)
 ac_add_options RUSTFLAGS='-C debuginfo=1'

--- a/mail/config/mozconfigs/macosx64/nightly
+++ b/mail/config/mozconfigs/macosx64/nightly
@@ -17,16 +17,16 @@ export MOZ_TELEMETRY_REPORTING=1
 # Package js shell
 export MOZ_PACKAGE_JSSHELL=1
 
 # 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
 
-ac_add_options --with-ccache
+. "$topsrcdir/build/mozconfig.cache"
 
 # 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
 
 # XXX hack to work around dsymutil failing on OSX builds (bug 1380381, 1382262)
 ac_add_options RUSTFLAGS='-C debuginfo=1'