diff --git a/lib/dml/mssql_native_moodle_database.php b/lib/dml/mssql_native_moodle_database.php
index 0b343f0bd18..cebe886481e 100644
--- a/lib/dml/mssql_native_moodle_database.php
+++ b/lib/dml/mssql_native_moodle_database.php
@@ -1257,7 +1257,7 @@ class mssql_native_moodle_database extends moodle_database {
 s only returning name of SQL substring function, it now requires all parameters.');
         }
         if ($length === false) {
-            return "SUBSTRING($expr, $start, (LEN($expr) - $start + 1))";
+            return "SUBSTRING($expr, $start, LEN($expr))";
         } else {
             return "SUBSTRING($expr, $start, $length)";
         }
diff --git a/lib/dml/sqlsrv_native_moodle_database.php b/lib/dml/sqlsrv_native_moodle_database.php
index a2232ab36e8..68efc62376c 100644
--- a/lib/dml/sqlsrv_native_moodle_database.php
+++ b/lib/dml/sqlsrv_native_moodle_database.php
@@ -1324,7 +1324,7 @@ class sqlsrv_native_moodle_database extends moodle_database {
         }
 
         if ($length === false) {
-            return "SUBSTRING($expr, $start, (LEN($expr) - $start + 1))";
+            return "SUBSTRING($expr, $start, LEN($expr))";
         } else {
             return "SUBSTRING($expr, $start, $length)";
         }