diff --git a/sites/all/modules/swftools/swftools.module b/sites/all/modules/swftools/swftools.module
index 54e09ed..591a5ec 100644
--- a/sites/all/modules/swftools/swftools.module
+++ b/sites/all/modules/swftools/swftools.module
@@ -497,9 +497,9 @@ function swf($file, $options = array()) {
   // all existing values by reference to allow optional override at the player.module level.
   if (module_hook($resolved_methods->player['module'], 'swftools_flashvars')) {
 
-    // Get player flashvars
-    $player_flashvars = module_invoke($resolved_methods->player['module'], 'swftools_flashvars', $action, $resolved_methods, $vars);
-    
+  // Get player flashvars - use a custom invoke to allow pass by reference
+  $player_flashvars = swftools_flashvars_invoke($action, $resolved_methods, $vars);
+
     // Merge player flashvars with existing flashvars
     if (is_array($player_flashvars)) {
       $vars->flashvars = array_merge($vars->flashvars, $player_flashvars);
@@ -1901,10 +1901,10 @@ function theme_swftools_formatter_playlist($element) {
         // Find out what the alternate formatter should be
         if ($formatter = _content_get_formatter($formatter_name, 'filefield')) {
           $theme = $formatter['module'] .'_formatter_'. $formatter_name;
-    
+
           // Theme the element according to the alternate formatter
           return theme($theme, $element[$child]);
-          
+
         }
     }
   }
@@ -1917,13 +1917,41 @@ function theme_swftools_formatter_playlist($element) {
       $files[] = $element[$key]['#item']['filepath'];
     }
   }
-  
+
   // If files array is empty then there is nothing to be rendered
   if (empty($files)) {
     return;
   }
-  
+
   // But if we got something then we can call swf() now to render it
   return swf($files);
-  
+
+}
+
+/**
+ * Invokes hook_swftools_flashvars() in the relevant player module.
+ *
+ * We cannot use module_invoke() for this, because the arguments need to be passed by reference.
+ *
+ * @param $action
+ *   String defining the action that is to be performed, eg SWFTOOLS_FLV_DISPLAY
+ * @param &$methods
+ *   Object containing two keys - player and method. Each consists of an array
+ *   that defines the details of the resolved player and embedding method that
+ *   is being used for this file.
+ * @param &$vars
+ *   Object containing three keys - othervars, flashvars and params. These are
+ *   arrays containing key/value pairs that contain all the data assigned to this
+ *   file so far. Refer to swf() for more details about the $vars array.
+ * @return
+ *   Return an array of flashvars needed to allow the player to work.
+ */
+function swftools_flashvars_invoke($action, &$methods, &$vars) {
+
+  // Build the name of the function we are going to call
+  $function = $methods->player['module'] . '_swftools_flashvars';
+
+  // Call the function and return the resulting flashvars to the caller
+  return($function($action, $methods, $vars));
+
 }