diff --git a/docs/usage/configuration-options.md b/docs/usage/configuration-options.md
index 2155e6dd28dc50a9eb9919d9acfeefdf46b7e3c2..1e6f5aa50d6e837c77a39326455328a40697270d 100644
--- a/docs/usage/configuration-options.md
+++ b/docs/usage/configuration-options.md
@@ -41,6 +41,10 @@ If a config option has a `parent` defined, it means it's only allowed to configu
 
 When an array or object configuration option is `mergeable`, it means that values inside it will be added to any existing object or array that existed with the same name.
 
+<!-- prettier-ignore -->
+!!! note
+    Config options with `type=string` are always non-mergeable, so `mergeable=false`.
+
 ---
 
 ## addLabels
diff --git a/docs/usage/self-hosted-configuration.md b/docs/usage/self-hosted-configuration.md
index 7168509723fbe981822f1a4cfeb0a3bf7fb8e46f..62c6508a6dbcefc7a09c41a4d4959030def625db 100644
--- a/docs/usage/self-hosted-configuration.md
+++ b/docs/usage/self-hosted-configuration.md
@@ -9,6 +9,10 @@ The configuration options listed in this document are applicable to self-hosted
 
 Please also see [Self-Hosted Experimental Options](./self-hosted-experimental.md).
 
+<!-- prettier-ignore -->
+!!! note
+    Config options with `type=string` are always non-mergeable, so `mergeable=false`.
+
 ## allowCustomCrateRegistries
 
 ## allowPlugins