diff --git a/replicated/config.yaml b/replicated/config.yaml
index 8260a703..d79d1084 100644
--- a/replicated/config.yaml
+++ b/replicated/config.yaml
@@ -675,10 +675,14 @@ spec:
           default: "0"
         - name: plugin_directory_marketplace_source
           title: Marketplace Source
-          help_text: "URI of the plugin catalog to load. Supports github://owner/repo[@ref], https:// URLs to a catalog JSON file, or file:// paths."
+          help_text: "URI of the plugin catalog to load. Supports github://owner/repo[@ref], or http(s):// URLs to a catalog JSON file."
           type: text
           when: 'repl{{ ConfigOptionEquals "plugin_directory_enabled" "1" }}'
           required: true
+          validation:
+            regex:
+              pattern: ^(github|https?)://
+              message: Must start with github://, https://, or http://
 
     - name: advanced_options
       title: Advanced Options