diff --git a/cache.inc.php b/cache.inc.php
index 6fce811..041223c 100644
--- a/cache.inc.php
+++ b/cache.inc.php
@@ -289,7 +289,11 @@ class ConfigCacheFileMap
   function update(array $added, array $removed)
   {
     foreach($added as $file)
-      $this->file2deps[$file] = [];
+    {
+      //TODO: are we sure about this check?
+      if(isset($this->file2deps[$file]))
+        $this->file2deps[$file] = [];
+    }
     foreach($removed as $file)
       unset($this->file2deps[$file]);
   }
@@ -361,6 +365,8 @@ class ConfigCacheUpdateParams
   function splitFilesByChunks(int $max_workers, bool $sort = true) : array
   {
     $flat = $this->affected_files->getFlatArray();
+    if(!$flat)
+      return array();
     if($sort)
       usort($flat, fn($a, $b) => $a[1] <=> $b[1]);
 
diff --git a/config.inc.php b/config.inc.php
index 4789c16..77ef68c 100644
--- a/config.inc.php
+++ b/config.inc.php
@@ -75,13 +75,19 @@ class ConfigManager
   }
 
   function getFileMap() : ConfigCacheFileMap
+  {
+    return $this->_getFileMap(null);
+  }
+
+  private function _getFileMap(?ConfigDirFiles $files = null) : ConfigCacheFileMap
   {
     if($this->file_map === null)
     {
       $map = $this->_tryLoadMap();
       if($map === null)
-        $map = $this->_makeMap($this->scanFiles(extension: '.js'));
+        $map = self::_makeMap($files ?? $this->scanFiles(extension: '.js'));
       $this->file_map = $map;
+      $this->_saveFileMap();
     }
     return $this->file_map;
   }
@@ -103,7 +109,7 @@ class ConfigManager
 
     $added_files = [];
     $removed_files = [];
-    $fs_cache_map = $this->_checkFileMap(
+    $this->_checkFileMap(
       $update_mode, 
       $input_files, 
       $added_files, 
@@ -113,7 +119,6 @@ class ConfigManager
     $affected_files = $this->_getAffectedFiles(
       $update_mode, 
       $result_bundle_file, 
-      $fs_cache_map, 
       $input_files, 
       $removed_files
     );
@@ -121,6 +126,8 @@ class ConfigManager
     //NOTE: at this poine taking into account only config files
     $affected_files->filter(fn($file) => str_ends_with($file, '.conf.js'));
 
+    config_log("Affected files: {$affected_files->count()}");
+
     $update_params = new ConfigCacheUpdateParams(
       globals: $this->globals, 
       affected_files: $affected_files, 
@@ -131,6 +138,8 @@ class ConfigManager
 
     $this->cache->clear();
 
+    $fs_cache_map = $this->getFileMap();
+
     //TODO: traverse all affected files and update file map
     foreach($affected_files as $file)
     {
@@ -141,39 +150,27 @@ class ConfigManager
     if($affected_files->count() > 0 || $added_files || $removed_files)
     {
       $fs_cache_map->update($added_files, $removed_files);
-      $this->_saveMap($fs_cache_map);
+      $this->_saveFileMap();
     }
 
     return $update_result;
   }
 
-  private function _checkFileMap(ConfigUpdateMode $update_mode, ConfigDirFiles $input_files, array &$added_files, array &$removed_files) : ConfigCacheFileMap
+  private function _checkFileMap(ConfigUpdateMode $update_mode, ConfigDirFiles $input_files, array &$added_files, array &$removed_files)
   {
-    $fs_cache_map = $this->file_map;
-    //NOTE: if there's no map so far we need to create one
-    if($fs_cache_map === null)
-    {
-      //let's re-use the input files
-      if($update_mode === ConfigUpdateMode::Full || $update_mode === ConfigUpdateMode::RelativeToBundle)
-        $tmp_files = $input_files;
-      else
-        $tmp_files = $this->scanFiles(extension: '.js');
-
-      $fs_cache_map = $this->_makeMap($tmp_files);
-      $this->file_map = $fs_cache_map;
-    }
+    $fs_cache_map = $this->_getFileMap($update_mode != ConfigUpdateMode::ChangedOnly ? $input_files : null);
 
     if($update_mode === ConfigUpdateMode::Full || $update_mode === ConfigUpdateMode::RelativeToBundle)
     {
       list($added_files, $removed_files) = $fs_cache_map->compare($input_files->getAllFiles());
       config_log("File map added: ".count($added_files).", removed: ".count($removed_files));
     }
-
-    return $fs_cache_map;
   }
 
-  private function _getAffectedFiles(ConfigUpdateMode $update_mode, ?string $result_bundle_file, ConfigCacheFileMap $fs_cache_map, ConfigDirFiles $input_files, array $removed_files) : ConfigDirFiles
+  private function _getAffectedFiles(ConfigUpdateMode $update_mode, ?string $result_bundle_file, ConfigDirFiles $input_files, array $removed_files) : ConfigDirFiles
   {
+    $fs_cache_map = $this->getFileMap();
+
     $affected_files = null;
 
     if($update_mode === ConfigUpdateMode::Full)
@@ -185,7 +182,7 @@ class ConfigManager
       if($result_bundle_file === null)
         throw new Exception("result_bundle_file argument is required");
 
-      $affected_files = $this->newDirFiles();
+      $affected_files = ConfigDirFiles::makeFor($this);
 
       foreach($input_files->getMap() as $base_dir => $files)
       {
@@ -217,17 +214,26 @@ class ConfigManager
         }
       }
     }
-    else
-      throw new Exception("Unknown update mode: {$update_mode->value}");
+    else if($update_mode === ConfigUpdateMode::ChangedOnly)
+    {
+      $affected_files = ConfigDirFiles::makeFor($this);
+
+      foreach($input_files as $file)
+      {
+        $affected_files->addFile($file, unique: true);
+
+        if(!str_ends_with($file, '.conf.js'))
+        {
+          $affected_by_file = $fs_cache_map->getAffectedFiles($file);
+          foreach($affected_by_file as $dep)
+            $affected_files->addFile($dep, unique: true);
+        }
+      }
+    }
 
     return $affected_files;
   }
 
-  function newDirFiles() : ConfigDirFiles
-  {
-    return new ConfigDirFiles([], $this->globals->base_dirs);
-  }
-
   function parseFile(string $file) : ConfigParseResult
   {
     return config_parse($this->globals->base_dirs, $file);
@@ -250,18 +256,17 @@ class ConfigManager
     return ConfigCacheFileMap::unserialize(ensure_read($this->_getMapPath()));
   }
 
-  private function _makeMap(ConfigDirFiles $files) : ConfigCacheFileMap
+  private static function _makeMap(ConfigDirFiles $files) : ConfigCacheFileMap
   {
     config_log("Creating file map");
     $map = new ConfigCacheFileMap();
     $map->update($files->getAllFiles(), []);
-    $this->_saveMap($map);
     return $map;
   }
 
-  private function _saveMap(ConfigCacheFileMap $map)
+  private function _saveFileMap()
   {
-    ensure_write($this->_getMapPath(), ConfigCacheFileMap::serialize($map));
+    ensure_write($this->_getMapPath(), ConfigCacheFileMap::serialize($this->getFileMap()));
   }
 }
 
diff --git a/scan.inc.php b/scan.inc.php
index 90f502f..bc16376 100644
--- a/scan.inc.php
+++ b/scan.inc.php
@@ -22,6 +22,11 @@ class ConfigDirFiles implements \ArrayAccess, \Countable, \Iterator
       $this->base_dirs = $base_dirs;
   }
 
+  static function makeFor(ConfigManager $mgr) : ConfigDirFiles
+  {
+    return new ConfigDirFiles([], $mgr->getGlobals()->base_dirs);
+  }
+
   function clear()
   {
     $this->base_dir2files = array();