diff --git a/modules/build/activation.nix b/modules/build/activation.nix
index 1979736..159bfe5 100644
--- a/modules/build/activation.nix
+++ b/modules/build/activation.nix
@@ -147,6 +147,7 @@ in
 
             ln --symbolic ${config.environment.files.login} $out/filesystem/bin/login
             ln --symbolic ${config.environment.files.loginInner} $out/filesystem/usr/lib/login-inner
+            ln --symbolic ${config.environment.files.prootStatic}/bin/proot-static $out/filesystem/bin/proot-static
 
             ln --symbolic ${config.environment.binSh} $out/filesystem/bin/sh
             ln --symbolic ${config.environment.usrBinEnv} $out/filesystem/usr/bin/env
diff --git a/modules/build/config.nix b/modules/build/config.nix
index c739cf1..b4d712f 100644
--- a/modules/build/config.nix
+++ b/modules/build/config.nix
@@ -12,6 +12,13 @@ with lib;
   options = {
 
     build = {
+      arch = mkOption {
+        type = types.enum [ "aarch64" "i686" ];
+        default = if pkgs.stdenv.isAarch64 then "aarch64" else "i686";
+        internal = true;
+        description = "Destination arch.";
+      };
+
       initialBuild = mkOption {
         type = types.bool;
         default = false;
diff --git a/modules/build/initial-build/default.nix b/modules/build/initial-build/default.nix
index bedcf53..95d6239 100644
--- a/modules/build/initial-build/default.nix
+++ b/modules/build/initial-build/default.nix
@@ -11,24 +11,17 @@ with lib;
 
   options = {
 
-    build = {
-      arch = mkOption {
-        type = types.enum [ "aarch64" "i686" ];
-        description = "Destination arch.";
+    build.channel = {
+      nixpkgs = mkOption {
+        type = types.str;
+        default = "https://nixos.org/channels/nixos-19.09";
+        description = "Channel URL for nixpkgs.";
       };
 
-      channel = {
-        nixpkgs = mkOption {
-          type = types.str;
-          default = "https://nixos.org/channels/nixos-19.09";
-          description = "Channel URL for nixpkgs.";
-        };
-
-        nix-on-droid = mkOption {
-          type = types.str;
-          default = "https://github.com/t184256/nix-on-droid-bootstrap/archive/master.tar.gz";
-          description = "Channel URL for nix-on-droid.";
-        };
+      nix-on-droid = mkOption {
+        type = types.str;
+        default = "https://github.com/t184256/nix-on-droid-bootstrap/archive/master.tar.gz";
+        description = "Channel URL for nix-on-droid.";
       };
     };
 
diff --git a/modules/environment/login/default.nix b/modules/environment/login/default.nix
index 4eb19a2..f1f04d5 100644
--- a/modules/environment/login/default.nix
+++ b/modules/environment/login/default.nix
@@ -6,6 +6,8 @@
 with lib;
 
 let
+  cfg = config.environment.files;
+
   login = pkgs.callPackage ./login.nix { inherit config; };
 
   loginInner = pkgs.callPackage ./login-inner.nix { inherit config customPkgs; };
@@ -31,6 +33,13 @@ in
         internal = true;
         description = "Login-inner script.";
       };
+
+      prootStatic = mkOption {
+        type = types.package;
+        readOnly = true;
+        internal = true;
+        description = "proot-static package.";
+      };
     };
 
   };
@@ -40,14 +49,26 @@ in
 
   config = {
 
-    build.activation.installLoginScripts = ''
-      $DRY_RUN_CMD mkdir $VERBOSE_ARG --parents /bin /usr/lib
-      $DRY_RUN_CMD cp $VERBOSE_ARG ${login} /bin/login
-      $DRY_RUN_CMD cp $VERBOSE_ARG ${loginInner} /usr/lib/login-inner
-    '';
+    build.activation = {
+      installLoginScripts = ''
+        $DRY_RUN_CMD mkdir $VERBOSE_ARG --parents /bin /usr/lib
+        $DRY_RUN_CMD cp $VERBOSE_ARG ${login} /bin/login
+        $DRY_RUN_CMD cp $VERBOSE_ARG ${loginInner} /usr/lib/login-inner
+      '';
+
+      installProotStatic = ''
+        $DRY_RUN_CMD mkdir $VERBOSE_ARG --parents /bin
+        $DRY_RUN_CMD cp $VERBOSE_ARG ${cfg.prootStatic}/bin/proot-static /bin/.proot-static.new
+      '';
+    };
 
     environment.files = {
       inherit login loginInner;
+
+      prootStatic =
+        if config.build.arch == "aarch64"
+        then "/nix/store/40zq5iy3iaj3pc9phshxmp4x8k7084lf-proot-termux-unstable-2019-09-05-aarch64-unknown-linux-android"
+        else "/nix/store/wlr4f16mfsg1fkj4wdrppcmh0kd3lgwv-proot-termux-unstable-2019-09-05-i686-unknown-linux-android";
     };
 
   };
diff --git a/modules/environment/login/login.nix b/modules/environment/login/login.nix
index a8d04a0..dc2d729 100644
--- a/modules/environment/login/login.nix
+++ b/modules/environment/login/login.nix
@@ -31,6 +31,10 @@ writeScript "login" ''
       exec ${installationDir}/bin/login "$@"
     ''
     else ''
+      if [[ -x ${installationDir}/bin/.proot-static.new ]] && ! $(/system/bin/pgrep proot-static); then
+        /system/bin/mv ${installationDir}/bin/.proot-static.new ${installationDir}/bin/proot-static
+      fi
+
       exec ${installationDir}/bin/proot-static \
         -b ${installationDir}/nix:/nix \
         -b ${installationDir}/bin:/bin \
diff --git a/pkgs/lib/load-nixpkgs.nix b/pkgs/lib/load-nixpkgs.nix
index 1ad68d4..2cf4342 100644
--- a/pkgs/lib/load-nixpkgs.nix
+++ b/pkgs/lib/load-nixpkgs.nix
@@ -8,6 +8,7 @@ let
   };
 
   # head of nixos-19.09 as of 2019-10-14
+  # note: when updating nixpkgs, update store paths of proot-termux in modules/environment/login/default.nix
   pinnedPkgsSrc = builtins.fetchTarball {
     url = "https://github.com/NixOS/nixpkgs/archive/45a25ff41a2309099ff2e70b2f37debd5e567618.tar.gz";
     sha256 = "0w37p98i47d7snhckz8a3a60v0f05b5047vsm4rczink9mk9x7r3";