diff --git a/sdk_container/src/third_party/coreos-overlay/profiles/coreos/base/package.use.mask b/sdk_container/src/third_party/coreos-overlay/profiles/coreos/base/package.use.mask
index 2e188858ea..c78b55a650 100644
--- a/sdk_container/src/third_party/coreos-overlay/profiles/coreos/base/package.use.mask
+++ b/sdk_container/src/third_party/coreos-overlay/profiles/coreos/base/package.use.mask
@@ -15,3 +15,10 @@ sys-boot/syslinux perl
 
 # not needed, problems building with GCC 7.3.0
 sys-libs/ncurses cxx
+
+# app-editors/nano with `USE=unicode` results in build failures in SDK
+# stage1, because ncurses >= 6.2_p20210619 which does not have the USE
+# flag at all.
+# To fix that, exclude the unicode USE flag from packages.use.force list,
+# which is defined in portage-stable.
+app-editors/nano unicode