diff --git a/CHANGELOG b/CHANGELOG
index 39d586733..53515f6d0 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,6 +1,7 @@
 CHANGELOG Roundcube Webmail
 ===========================
 
+- Fix default_port option handling in Installer when config.inc.php file exists (#1487925)
 - Removed option focus_on_new_message, added newmail_notifier plugin
 - Added general rcube_cache class with Memcache and APC support
 - Improved caching performance by skipping writes of unchanged data
diff --git a/installer/index.php b/installer/index.php
index e09b82797..8df7ab0ef 100644
--- a/installer/index.php
+++ b/installer/index.php
@@ -41,7 +41,7 @@ if ($RCI->configured && ($RCI->getprop('enable_installer') || $_SESSION['allowin
 
   header('Content-type: text/plain');
   header('Content-Disposition: attachment; filename="'.$filename.'"');
-  
+
   $RCI->merge_config();
   echo $RCI->create_config($_GET['_mergeconfig'], true);
   exit;
diff --git a/installer/rcube_install.php b/installer/rcube_install.php
index 8ff6492d2..c8c103a95 100644
--- a/installer/rcube_install.php
+++ b/installer/rcube_install.php
@@ -123,8 +123,8 @@ class rcube_install
     
     return $value !== null && $value !== '' ? $value : $default;
   }
-  
-  
+
+
   /**
    * Take the default config file and replace the parameters
    * with the submitted form data
@@ -135,13 +135,14 @@ class rcube_install
   function create_config($which, $force = false)
   {
     $out = @file_get_contents(RCMAIL_CONFIG_DIR . "/{$which}.inc.php.dist");
-    
+
     if (!$out)
       return '[Warning: could not read the config template file]';
 
     foreach ($this->config as $prop => $default) {
+
       $value = (isset($_POST["_$prop"]) || $this->bool_config_props[$prop]) ? $_POST["_$prop"] : $default;
-      
+
       // convert some form data
       if ($prop == 'debug_level') {
         $val = 0;
@@ -193,9 +194,9 @@ class rcube_install
       else if (is_numeric($value)) {
         $value = intval($value);
       }
-      
+
       // skip this property
-      if (!$force && ($value == $default))
+      if (!$force && !$this->configured && ($value == $default))
         continue;
 
       // save change