diff --git a/README.md b/README.md
index 8db01bc..822474b 100644
--- a/README.md
+++ b/README.md
@@ -110,7 +110,7 @@ make install    # DESTDIR/PREFIX staged install incl. the packaging/ files
 packaging/make-sysroot.sh                  # one-time: Alpine aarch64 sysroot from the CDN
 crafter-build -- --target=aarch64-alpine-linux-musl \
     --sysroot=$HOME/.cache/imsd/sysroot-aarch64-alpine \
-    --march=armv8-a --mtune=generic
+    --march=armv8.6-a+fp16fml+aes+sha3+sm4 --mtune=cortex-a720
 # same flags after `crafter-build test --target=aarch64-alpine-linux-musl`
 # run the suite under qemu-aarch64 against the sysroot
 ```
diff --git a/packaging/build-package.sh b/packaging/build-package.sh
index e035173..ae45bf6 100755
--- a/packaging/build-package.sh
+++ b/packaging/build-package.sh
@@ -75,7 +75,11 @@ retry "make sysroot" "$SRC/packaging/make-sysroot.sh" "$SYSROOT"
 # host arch — the aarch64 binaries are additionally exercised by fp6-img's
 # chroot `make check` whenever an image builds)
 cd "$SRC"
-XTARGET="--target=aarch64-alpine-linux-musl --sysroot=$SYSROOT --march=armv8-a --mtune=generic"
+# The phone is one SoC, 4x Cortex-A520 + 4x Cortex-A720, so build for it.
+# armv8.6-a is the highest level whose mandatory set it exposes (8.7 would
+# assume WFxT, 9.x SVE2 - neither is in its hwcaps); +fp16fml+aes+sha3+sm4 are
+# the optional extensions it has. Same string as the fp6-img aports.
+XTARGET="--target=aarch64-alpine-linux-musl --sysroot=$SYSROOT --march=armv8.6-a+fp16fml+aes+sha3+sm4 --mtune=cortex-a720"
 crafter-build -- $XTARGET
 crafter-build -- --product=media $XTARGET
 crafter-build -- --product=dialerd $XTARGET