diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index f9005ef..e08c908 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -39,4 +39,7 @@ Then you can edit the files as normal and reload the page.
 
 ## Notes
 
-1. For configuration, please note, we now use a `dev` environment config file: `_config_dev.yml`
+1. For configuration, please note, we now use a `dev` environment config file:
+   `_config_dev.yml`. Hence if you edit one `_config*` file and you also want
+   that change to be reflected in the other environment ("dev", "prod") then
+   edit the other file as well!