diff --git a/inc/confutils.php b/inc/confutils.php
index 4035d6dd4a2c08716219191004a805d9774b19c4..8b61a8d5b5b30f7c5758b1b4d3e570afba88aefe 100644
--- a/inc/confutils.php
+++ b/inc/confutils.php
@@ -206,6 +206,11 @@ function confToHash($file,$lower=false) {
  * @param  string   $type     the configuration settings to be read, must correspond to a key/array in $config_cascade
  * @param  callback $fn       the function used to process the configuration file into an array
  * @param  array    $params   optional additional params to pass to the callback
+ * @param  callback $combine  the function used to combine arrays of values read from different configuration files;
+ *                            the function takes two parameters,
+ *                               $combined - the already read & merged configuration values
+ *                               $new - array of config values from the config cascade file being currently processed
+ *                            and returns an array of the merged configuration values.
  * @return array    configuration values
  */
 function retrieveConfig($type,$fn,$params=null,$combine='array_merge') {