diff --git a/modules/default.nix b/modules/default.nix
index f6a3ee5..b921445 100644
--- a/modules/default.nix
+++ b/modules/default.nix
@@ -1,26 +1,26 @@
 # Licensed under GNU Lesser General Public License v3 or later, see COPYING.
 # Copyright (c) 2019 Alexander Sosedkin and other contributors, see AUTHORS.
 
-{ pkgs ? import <nixpkgs> { }, initialBuild ? false, config ? { } }:
+{ pkgs ? import <nixpkgs> { }, config ? null }:
 
 with pkgs.lib;
 
 let
-  homeDir = builtins.getEnv "HOME";
-  configFile = homeDir + "/.config/nixpkgs/nix-on-droid.nix";
+  defaultConfigFile = "${builtins.getEnv "HOME"}/.config/nixpkgs/nix-on-droid.nix";
 
-  hasConfigFile = builtins.pathExists configFile;
+  configModule =
+    if config != null                             then config
+    else if builtins.pathExists defaultConfigFile then defaultConfigFile
+    else if pkgs.config ? nix-on-droid            then pkgs.config.nix-on-droid
+    else throw "No config file found! Create one in ~/.config/nixpkgs/nix-on-droid.nix";
 
   rawModule = evalModules {
     modules = [
       {
         _module.args = { inherit pkgs; };
       }
-    ]
-    ++ optional (!initialBuild && hasConfigFile) configFile
-    ++ optional (!initialBuild && !hasConfigFile && pkgs.config ? nix-on-droid) pkgs.config.nix-on-droid
-    ++ optional initialBuild config
-    ++ import ./module-list.nix;
+      configModule
+    ] ++ import ./module-list.nix;
   };
 
   failedAssertions = map (x: x.message) (filter (x: !x.assertion) rawModule.config.assertions);
diff --git a/nix-on-droid/nix-on-droid.sh b/nix-on-droid/nix-on-droid.sh
index 784ec6a..9cef2cb 100644
--- a/nix-on-droid/nix-on-droid.sh
+++ b/nix-on-droid/nix-on-droid.sh
@@ -23,6 +23,7 @@ function doHelp() {
     echo "  -h|--help       Print this help"
     echo "  -n|--dry-run    Do a dry run, only prints what actions would be taken"
     echo "  -v|--verbose    Verbose output"
+    echo "  -f|--file       Path to config file"
     echo
     echo "Options passed on to nix build"
     echo
@@ -52,6 +53,10 @@ function doSwitch() {
         PASSTHROUGH_OPTS+=(--show-trace)
     fi
 
+    if [[ -n "$CONFIG_FILE" ]]; then
+        PASSTHROUGH_OPTS+=(--argstr config "$(realpath "$CONFIG_FILE")")
+    fi
+
     echo "Building activation package..."
     nix build \
         --no-link \
@@ -86,6 +91,7 @@ function doSwitchGeneration() {
 COMMAND=
 COMMAND_ARGS=()
 PASSTHROUGH_OPTS=()
+CONFIG_FILE=
 
 while [[ $# -gt 0 ]]; do
     opt="$1"
@@ -94,6 +100,10 @@ while [[ $# -gt 0 ]]; do
         generations|help|rollback|switch|switch-generation)
             COMMAND="$opt"
             ;;
+        -f|--file)
+            CONFIG_FILE="$1"
+            shift
+            ;;
         -h|--help)
             doHelp
             exit 0
diff --git a/pkgs/default.nix b/pkgs/default.nix
index d6bd45a..b8f70af 100644
--- a/pkgs/default.nix
+++ b/pkgs/default.nix
@@ -10,7 +10,6 @@ let
 
   modules = import ../modules {
     pkgs = nixpkgs;
-    initialBuild = true;
 
     config = {
       imports = [ ../modules/build/initial-build.nix ];