diff --git a/lib/external/classes/external_api.php b/lib/external/classes/external_api.php
index c770a80ab71..2bb29c7e42f 100644
--- a/lib/external/classes/external_api.php
+++ b/lib/external/classes/external_api.php
@@ -67,7 +67,8 @@ class external_api {
             }
             if (!file_exists($function->classpath)) {
                 throw new coding_exception(
-                    "Cannot find file {$function->classpath} with external function implementation"
+                    "Cannot find file {$function->classpath} with external function implementation " .
+                        "for {$function->classname}::{$function->methodname}"
                 );
             }
             require_once($function->classpath);