diff --git a/core/modules/migrate/src/Plugin/migrate/process/Substr.php b/core/modules/migrate/src/Plugin/migrate/process/Substr.php
index aea79121cd303bfc0c615a1dedb8f581a30b13f8..d97c3ba51a78babde8d6a584469ebd1c6c149a9e 100644
--- a/core/modules/migrate/src/Plugin/migrate/process/Substr.php
+++ b/core/modules/migrate/src/Plugin/migrate/process/Substr.php
@@ -55,7 +55,6 @@
  *      source: some_text_field
  *    -
  *      plugin: substr
- *      source: some_text_field
  *      start: 6
  *      length: 10
  * @endcode