diff --git a/core/assets/scaffold/files/default.services.yml b/core/assets/scaffold/files/default.services.yml
index 0b3b7414895e8bf6f51fb95c06da7a03cd49cbdb..873fc7303f6235817d2ce4b7f008227b83e60912 100644
--- a/core/assets/scaffold/files/default.services.yml
+++ b/core/assets/scaffold/files/default.services.yml
@@ -204,7 +204,8 @@ parameters:
     allowedHeaders: []
     # Specify allowed request methods, specify ['*'] to allow all possible ones.
     allowedMethods: []
-    # Configure requests allowed from specific origins.
+    # Configure requests allowed from specific origins. Do not include trailing
+    # slashes with URLs.
     allowedOrigins: ['*']
     # Sets the Access-Control-Expose-Headers header.
     exposedHeaders: false
diff --git a/sites/default/default.services.yml b/sites/default/default.services.yml
index 0b3b7414895e8bf6f51fb95c06da7a03cd49cbdb..873fc7303f6235817d2ce4b7f008227b83e60912 100644
--- a/sites/default/default.services.yml
+++ b/sites/default/default.services.yml
@@ -204,7 +204,8 @@ parameters:
     allowedHeaders: []
     # Specify allowed request methods, specify ['*'] to allow all possible ones.
     allowedMethods: []
-    # Configure requests allowed from specific origins.
+    # Configure requests allowed from specific origins. Do not include trailing
+    # slashes with URLs.
     allowedOrigins: ['*']
     # Sets the Access-Control-Expose-Headers header.
     exposedHeaders: false