diff --git a/sdk_container/src/third_party/coreos-overlay/sys-fs/mdadm/mdadm-4.1.ebuild b/sdk_container/src/third_party/coreos-overlay/sys-fs/mdadm/mdadm-4.1.ebuild
index b6381aa4a0..60b9f601c9 100644
--- a/sdk_container/src/third_party/coreos-overlay/sys-fs/mdadm/mdadm-4.1.ebuild
+++ b/sdk_container/src/third_party/coreos-overlay/sys-fs/mdadm/mdadm-4.1.ebuild
@@ -16,8 +16,8 @@ SRC_URI="https://www.kernel.org/pub/linux/utils/raid/mdadm/${P/_/-}.tar.xz
 
 LICENSE="GPL-2"
 SLOT="0"
-[[ "${PV}" = *_rc* ]] || \
-KEYWORDS="~alpha amd64 arm ~arm64 hppa ~ia64 ~mips ppc ppc64 sparc x86"
+# Flatcar: Build for arm64 too.
+KEYWORDS="~alpha amd64 arm arm64 hppa ~ia64 ~mips ppc ppc64 sparc x86"
 IUSE="static"
 
 DEPEND="virtual/pkgconfig