diff --git a/aports/device/device-nokia-rx51/APKBUILD b/aports/device/device-nokia-rx51/APKBUILD
index 8420e4de..1962f10c 100644
--- a/aports/device/device-nokia-rx51/APKBUILD
+++ b/aports/device/device-nokia-rx51/APKBUILD
@@ -1,6 +1,6 @@
 pkgname=device-nokia-rx51
 pkgver=1
-pkgrel=15
+pkgrel=16
 pkgdesc="Nokia N900"
 url="https://github.com/postmarketOS"
 arch="noarch"
@@ -56,7 +56,7 @@ package() {
                 "$pkgdir"/usr/share/bkeymaps/us/rx51_us.bmap.gz
 }
 
-sha512sums="cecba9a4a5ba6ddd736e4a46eecac20865d6c4d7a2d95efbbc33d1e8cacf9e3583aa80118fd5044da6ee08997d9d2c59af4f896692859b6e2e39e55fa515b566  deviceinfo
+sha512sums="998790a43f6994ef919ac5b629ef23d76e3bcdf5e80987af996bec71c86bace7510e1ca59c20b14faf79dc986ad8c74c5cb5c44c9043905e877ebecc06232b4c  deviceinfo
 1b89309dd4fe7ee0ba37c6224a0152d6864bb1c7bc4e96918a57e01bebc4173559855ae9673887223de4a8baa3191c8ad88ec8594776a4110cdb19a7be790db4  uboot-script.cmd
 3d55e34b95791636e44a5f41754f3d0de039dbba41f7a556d43a95c9e64afcfa930046b4b96b40020b6f196096ffba93514682927e32fa4488686fdd19c6da5a  backlight-enable.sh
 98c554a709d6e8da5835bd792d833355d830fca1cfea12ec7fe4f41d1d1126389c51a8a392a7f94093473c19263cc6846cc40d7e179c2facf12db2d68ff923f9  90-touchscreen-dev.rules
diff --git a/aports/device/device-nokia-rx51/deviceinfo b/aports/device/device-nokia-rx51/deviceinfo
index dee1a98c..f90fd535 100644
--- a/aports/device/device-nokia-rx51/deviceinfo
+++ b/aports/device/device-nokia-rx51/deviceinfo
@@ -9,7 +9,7 @@ deviceinfo_keyboard="true"
 deviceinfo_keymaps="us/rx51_us"
 deviceinfo_nonfree="????"
 deviceinfo_dtb="omap3-n900"
-deviceinfo_modules_initfs="tsc2005 tsc200x-core omap_wdt twl4030_wdt"
+deviceinfo_modules_initfs="tsc2005 tsc200x-core omap_wdt twl4030_wdt omap-sham"
 deviceinfo_external_disk="true"
 deviceinfo_external_disk_install="true"
 deviceinfo_flash_methods="0xFFFF"
diff --git a/pmb/config/__init__.py b/pmb/config/__init__.py
index f7f7aab3..d1f9a37c 100644
--- a/pmb/config/__init__.py
+++ b/pmb/config/__init__.py
@@ -60,7 +60,11 @@ defaults = {
 
     # aes-xts-plain64 would be better, but this is not supported on LineageOS
     # kernel configs
-    "cipher": "aes-cbc-plain64"
+    "cipher": "aes-cbc-plain64",
+    # A higher value is typically desired, but this can lead to VERY long open
+    # times on slower devices due to host systems being MUCH faster than the
+    # target device: <https://github.com/postmarketOS/pmbootstrap/issues/429>
+    "iter_time": "200"
 }
 
 #
diff --git a/pmb/install/format.py b/pmb/install/format.py
index 24cd1028..f5b4aa9c 100644
--- a/pmb/install/format.py
+++ b/pmb/install/format.py
@@ -40,7 +40,8 @@ def format_and_mount_root(args):
         logging.info(
             " *** TYPE IN THE FULL DISK ENCRYPTION PASSWORD (TWICE!) ***")
         pmb.chroot.root(args, ["cryptsetup", "luksFormat", "--use-urandom",
-                               "--cipher", args.cipher, "-q", device], log=False)
+                               "--cipher", args.cipher, "-q", device,
+                               "--iter-time", args.iter_time], log=False)
         pmb.chroot.root(args, ["cryptsetup", "luksOpen", device,
                                "pm_crypt"], log=False)
         if not os.path.exists(args.work + "/chroot_native" + mountpoint):
diff --git a/pmb/parse/arguments.py b/pmb/parse/arguments.py
index e5976fd9..84267414 100644
--- a/pmb/parse/arguments.py
+++ b/pmb/parse/arguments.py
@@ -203,6 +203,9 @@ def arguments():
                          " eg. /dev/mmcblk0")
     install.add_argument("--cipher", help="cryptsetup cipher used to"
                          " encrypt the system partition, eg. aes-xts-plain64")
+    install.add_argument("--iter-time", help="cryptsetup iteration time (in"
+                         " miliseconds) to use when encrypting the system"
+                         " partiton")
     install.add_argument("--add", help="comma separated list of packages to be"
                          " added to the rootfs (e.g. 'vim,gcc')")
     install.add_argument("--no-fde", help="do not use full disk encryption",
@@ -218,7 +221,7 @@ def arguments():
                          action="store_true", dest="recovery_flash_bootimg")
     install.add_argument("--recovery-install-partition", default="system",
                          help="partition to flash from recovery,"
-                              "eg. external_sd",
+                              " eg. external_sd",
                          dest="recovery_install_partition")
 
     # Action: menuconfig / parse_apkbuild