diff --git a/lib/dml/moodle_database.php b/lib/dml/moodle_database.php
index ca376eb499c..cf303a51818 100644
--- a/lib/dml/moodle_database.php
+++ b/lib/dml/moodle_database.php
@@ -1752,7 +1752,7 @@ abstract class moodle_database {
     }
 
     /**
-     * Returns the proper substr() function for each DB.
+     * Returns the proper substr() SQL text used to extract substrings from DB
      * NOTE: this was originally returning only function name
      *
      * @param string $expr some string field, no aggregates
diff --git a/lib/dml/mssql_native_moodle_database.php b/lib/dml/mssql_native_moodle_database.php
index c524021a974..1b58238c927 100644
--- a/lib/dml/mssql_native_moodle_database.php
+++ b/lib/dml/mssql_native_moodle_database.php
@@ -1139,7 +1139,7 @@ class mssql_native_moodle_database extends moodle_database {
     }
 
     /**
-     * Returns the proper substr() function for each DB.
+     * Returns the proper substr() SQL text used to extract substrings from DB
      * NOTE: this was originally returning only function name
      *
      * @param string $expr some string field, no aggregates