diff --git a/structure/ws_to_ts_functions.php b/structure/ws_to_ts_functions.php
index ef11eab0..3869a6e9 100644
--- a/structure/ws_to_ts_functions.php
+++ b/structure/ws_to_ts_functions.php
@@ -18,13 +18,26 @@
  * Helper functions for converting a Moodle WS structure to a TS type.
  */
 
-use core_external\external_api;
-use core_external\external_function_parameters;
-use core_external\external_value;
-use core_external\external_warnings;
-use core_external\external_files;
-use core_external\external_single_structure;
-use core_external\external_multiple_structure;
+ if (file_exists("$CFG->libdir/external/classes/external_api.php")) {
+    use core_external\external_api;
+    use core_external\external_function_parameters;
+    use core_external\external_value;
+    use core_external\external_warnings;
+    use core_external\external_files;
+    use core_external\external_single_structure;
+    use core_external\external_multiple_structure;
+} else {
+    require_once("$CFG->libdir/externallib.php");
+
+    use external_api;
+    use external_function_parameters;
+    use external_value;
+    use external_warnings;
+    use external_files;
+    use external_single_structure;
+    use external_multiple_structure;
+ }
+
 
 /**
  * Get the structure of a WS params or returns.