diff --git a/CRM/Upgrade/Incremental/php/FiveThirtySeven.php b/CRM/Upgrade/Incremental/php/FiveThirtySeven.php
index bad13a5b51dda39f2eb8c63b2a371f96a09a1381..3f4ea75796eae4f593e116746024d29744d386c8 100644
--- a/CRM/Upgrade/Incremental/php/FiveThirtySeven.php
+++ b/CRM/Upgrade/Incremental/php/FiveThirtySeven.php
@@ -16,8 +16,8 @@ class CRM_Upgrade_Incremental_php_FiveThirtySeven extends CRM_Upgrade_Incrementa
   /**
    * Compute any messages which should be displayed beforeupgrade.
    *
-   * Note: This function is called iteratively for each upcoming
-   * revision to the database.
+   * Note: This function is called iteratively for each incremental upgrade step.
+   * There must be a concrete step (eg 'X.Y.Z.mysql.tpl' or 'upgrade_X_Y_Z()').
    *
    * @param string $preUpgradeMessage
    * @param string $rev
@@ -34,6 +34,9 @@ class CRM_Upgrade_Incremental_php_FiveThirtySeven extends CRM_Upgrade_Incrementa
   /**
    * Compute any messages which should be displayed after upgrade.
    *
+   * Note: This function is called iteratively for each incremental upgrade step.
+   * There must be a concrete step (eg 'X.Y.Z.mysql.tpl' or 'upgrade_X_Y_Z()').
+   *
    * @param string $postUpgradeMessage
    *   alterable.
    * @param string $rev
diff --git a/CRM/Upgrade/Incremental/php/Template.php b/CRM/Upgrade/Incremental/php/Template.php
index 3f9d3971dccad330613a74e68fb7399cf166e4dc..debafbfa8a84b2d972def52ef19b629d8ad42565 100644
--- a/CRM/Upgrade/Incremental/php/Template.php
+++ b/CRM/Upgrade/Incremental/php/Template.php
@@ -22,8 +22,8 @@ class CRM_Upgrade_Incremental_php_<?php echo $camelNumber; ?> extends CRM_Upgrad
   /**
    * Compute any messages which should be displayed beforeupgrade.
    *
-   * Note: This function is called iteratively for each upcoming
-   * revision to the database.
+   * Note: This function is called iteratively for each incremental upgrade step.
+   * There must be a concrete step (eg 'X.Y.Z.mysql.tpl' or 'upgrade_X_Y_Z()').
    *
    * @param string $preUpgradeMessage
    * @param string $rev
@@ -40,6 +40,9 @@ class CRM_Upgrade_Incremental_php_<?php echo $camelNumber; ?> extends CRM_Upgrad
   /**
    * Compute any messages which should be displayed after upgrade.
    *
+   * Note: This function is called iteratively for each incremental upgrade step.
+   * There must be a concrete step (eg 'X.Y.Z.mysql.tpl' or 'upgrade_X_Y_Z()').
+   *
    * @param string $postUpgradeMessage
    *   alterable.
    * @param string $rev