diff --git a/app.php b/app.php
index 8176ebec..2a586885 100644
--- a/app.php
+++ b/app.php
@@ -12,6 +12,7 @@ require_once __DIR__ . '/vendor/autoload.php';
 // Load config files
 require_once GROCY_DATAPATH . '/config.php';
 require_once __DIR__ . '/config-dist.php'; // For not in own config defined values we use the default ones
+require_once __DIR__ . '/helpers/ConfigurationValidator.php';
 
 // Definitions for dev/demo/prerelease mode
 if ((GROCY_MODE === 'dev' || GROCY_MODE === 'demo' || GROCY_MODE === 'prerelease') && !defined('GROCY_USER_ID'))
@@ -31,6 +32,16 @@ if (GROCY_DISABLE_AUTH === true)
 	define('GROCY_SHOW_AUTH_VIEWS', false);
 }
 
+// Check if any invalid entries in config.php have been made
+try
+{
+	(new ConfigurationValidator())->validateConfig();
+}
+catch (EInvalidConfig $ex)
+{
+	exit('Invalid setting in config.php: ' . $ex->getMessage());
+}
+
 // Setup base application
 AppFactory::setContainer(new DI\Container());
 $app = AppFactory::create();
diff --git a/helpers/ConfigurationValidator.php b/helpers/ConfigurationValidator.php
new file mode 100644
index 00000000..f3d6ec19
--- /dev/null
+++ b/helpers/ConfigurationValidator.php
@@ -0,0 +1,87 @@
+<?php
+
+class EInvalidConfig extends Exception
+{
+}
+
+class ConfigurationValidator
+{
+	public function validateConfig()
+	{
+		self::checkMode();
+		self::checkDefaultLocale();
+		self::checkCurrencyFormat();
+		self::checkFirstDayOfWeek();
+		self::checkEntryPage();
+		self::checkMealplanFirstDayOfWeek();
+		self::checkAutoNightModeRange();
+	}
+
+
+	private function checkMode()
+	{
+		$allowedModes = ["production", "dev", "demo", "prerelease"];
+		if (!in_array(GROCY_MODE, $allowedModes))
+		{
+			throw new EInvalidConfig('Invalid mode "' . GROCY_MODE . '" set, only ' . implode(", ", $allowedModes) . " allowed");
+		}
+	}
+
+	private function checkDefaultLocale()
+	{
+		if (!file_exists(__DIR__ . "/../localization/" . GROCY_DEFAULT_LOCALE))
+		{
+			throw new EInvalidConfig('Invalid locale "'. GROCY_DEFAULT_LOCALE . '" set, locale needs to exist in folder localization');
+		}
+	}
+
+	private function checkFirstDayOfWeek()
+	{
+		if (!(GROCY_CALENDAR_FIRST_DAY_OF_WEEK == "" ||
+			(is_numeric(GROCY_CALENDAR_FIRST_DAY_OF_WEEK) && GROCY_CALENDAR_FIRST_DAY_OF_WEEK >= 0 && GROCY_CALENDAR_FIRST_DAY_OF_WEEK <= 6)))
+		{
+			throw new EInvalidConfig('Invalid value for CALENDAR_FIRST_DAY_OF_WEEK');
+		}
+	}
+
+	private function checkCurrencyFormat()
+	{
+		if (!(preg_match("/^([A-z]){3}$/", GROCY_CURRENCY)))
+		{
+			throw new EInvalidConfig('CURRENCY is not in ISO 4217 format (three letter code)');
+		}
+	}
+
+	private function checkEntryPage()
+	{
+		$allowedPages = ["stock", "shoppinglist", "recipes", "chores", "tasks", "batteries", "equipment", "calendar", "mealplan"];
+		if (!in_array(GROCY_ENTRY_PAGE, $allowedPages))
+		{
+			throw new EInvalidConfig('Invalid entry page "' . GROCY_ENTRY_PAGE . '" set, only ' . implode(", ", $allowedPages) . " allowed");
+		}
+	}
+
+	private function checkMealplanFirstDayOfWeek()
+	{
+		if (!(GROCY_MEAL_PLAN_FIRST_DAY_OF_WEEK == "" ||
+			(is_numeric(GROCY_MEAL_PLAN_FIRST_DAY_OF_WEEK) &&GROCY_MEAL_PLAN_FIRST_DAY_OF_WEEK >= 0 && GROCY_MEAL_PLAN_FIRST_DAY_OF_WEEK <= 6)))
+		{
+			throw new EInvalidConfig('Invalid value for MEAL_PLAN_FIRST_DAY_OF_WEEK');
+		}
+	}
+
+
+	private function checkAutoNightModeRange()
+	{
+		global $GROCY_DEFAULT_USER_SETTINGS;
+		if (!(preg_match("/^(?:2[0-3]|[01][0-9]):[0-5][0-9]$/", $GROCY_DEFAULT_USER_SETTINGS["auto_night_mode_time_range_from"])))
+		{
+			throw new EInvalidConfig('auto_night_mode_time_range_from is not in HH:mm format ('.$GROCY_DEFAULT_USER_SETTINGS["auto_night_mode_time_range_from"].')');
+		}
+		if (!(preg_match("/^(?:2[0-3]|[01][0-9]):[0-5][0-9]$/", $GROCY_DEFAULT_USER_SETTINGS["auto_night_mode_time_range_to"])))
+		{
+			throw new EInvalidConfig('auto_night_mode_time_range_to is not in HH:mm format ('.$GROCY_DEFAULT_USER_SETTINGS["auto_night_mode_time_range_to"].')');
+		}
+	}
+
+}