diff --git a/doc/ci/yaml/README.md b/doc/ci/yaml/README.md
index 66743ea0e47..02f198dbd67 100644
--- a/doc/ci/yaml/README.md
+++ b/doc/ci/yaml/README.md
@@ -1634,6 +1634,10 @@ rspec:
     - bundle exec rspec
 ```
 
+NOTE: **Note:**
+`include` requires the external YAML files to have the extensions `.yml` or `.yaml`. 
+The external file will not be included if the extension is missing.
+
 You can define it either as a single string, or, in case you want to include
 more than one files, an array of different values . The following examples
 are both valid cases: