diff --git a/.gitignore b/.gitignore
index 7d23e93..9b8d154 100644
--- a/.gitignore
+++ b/.gitignore
@@ -38,3 +38,7 @@ Thumbs.db
 *~
 *.lock
 *.out
+
+# App specific #
+################
+config.php
\ No newline at end of file
diff --git a/README.markdown b/README.markdown
index e9b1100..bb00576 100644
--- a/README.markdown
+++ b/README.markdown
@@ -118,3 +118,25 @@ You can report feeds that doesn't works properly too.
 Miniflux is tested with the latest versions of Mozilla Firefox, Google Chrome and Safari.
 
 I don't use Microsoft products, then I have no idea if Miniflux works correctly with Internet Explorer.
+
+### How to override application variables?
+
+There is few settings that can't be changed by the user interface.
+These parameters are defined with PHP constants.
+
+To override them, create a `config.php` file at the root of the project and change yourself the values.
+
+By example, to override the default HTTP timeout value:
+
+    # file config.php
+
+    <?php
+
+    // My specific HTTP timeout (5 seconds)
+    define('HTTP_TIMEOUT', 5);
+
+Actually, the following constants can be overrided:
+
+- `HTTP_TIMEOUT` => default value is 10 seconds
+- `APP_VERSION` => default value is master
+- `DB_FILENAME` => default value is `data/db.sqlite`
diff --git a/common.php b/common.php
index 3e9ad9e..fc85c59 100644
--- a/common.php
+++ b/common.php
@@ -9,26 +9,20 @@ require 'vendor/PicoDb/Table.php';
 require 'schema.php';
 require 'model.php';
 
+if (file_exists('config.php')) require 'config.php';
 
-const DB_VERSION     = 9;
-const APP_VERSION    = 'master';
-const HTTP_TIMEOUT   = 10;
-
-
-function get_db_filename()
-{
-    return 'data/db.sqlite';
-}
-
+defined('APP_VERSION') or define('APP_VERSION', 'master');
+defined('HTTP_TIMEOUT') or define('HTTP_TIMEOUT', 10);
+defined('DB_FILENAME') or define('DB_FILENAME', 'data/db.sqlite');
 
 PicoTools\container('db', function() {
 
     $db = new PicoDb\Database(array(
         'driver' => 'sqlite',
-        'filename' => get_db_filename()
+        'filename' => DB_FILENAME
     ));
 
-    if ($db->schema()->check(DB_VERSION)) {
+    if ($db->schema()->check(Model\DB_VERSION)) {
 
         return $db;
     }
diff --git a/index.php b/index.php
index 732eaee..49203a9 100644
--- a/index.php
+++ b/index.php
@@ -394,7 +394,7 @@ Router\get_action('optimize-db', function() {
 Router\get_action('download-db', function() {
 
     Response\force_download('db.sqlite.gz');
-    Response\binary(gzencode(file_get_contents(get_db_filename())));
+    Response\binary(gzencode(file_get_contents(DB_FILENAME)));
 });
 
 
@@ -439,7 +439,7 @@ Router\get_action('config', function() {
     Response\html(Template\layout('config', array(
         'errors' => array(),
         'values' => Model\get_config(),
-        'db_size' => filesize(get_db_filename()),
+        'db_size' => filesize(DB_FILENAME),
         'languages' => Model\get_languages(),
         'autoflush_options' => Model\get_autoflush_options(),
         'paging_options' => Model\get_paging_options(),
@@ -472,7 +472,7 @@ Router\post_action('config', function() {
     Response\html(Template\layout('config', array(
         'errors' => $errors,
         'values' => $values,
-        'db_size' => filesize(get_db_filename()),
+        'db_size' => filesize(DB_FILENAME),
         'languages' => Model\get_languages(),
         'autoflush_options' => Model\get_autoflush_options(),
         'paging_options' => Model\get_paging_options(),
diff --git a/model.php b/model.php
index 9ed09ad..65928ad 100644
--- a/model.php
+++ b/model.php
@@ -22,6 +22,7 @@ use PicoFeed\Reader;
 use PicoFeed\Export;
 
 
+const DB_VERSION     = 9;
 const HTTP_USERAGENT = 'Miniflux - http://miniflux.net';
 const LIMIT_ALL      = -1;