diff --git a/code/web/release_notes/24.12.00.MD b/code/web/release_notes/24.12.00.MD
index ac6bdf7c40..6279ea1ea0 100644
--- a/code/web/release_notes/24.12.00.MD
+++ b/code/web/release_notes/24.12.00.MD
@@ -67,6 +67,7 @@
 
 ### Other Updates
 - Redirect to selfRegistrationUrl if the /MyAccount/SelfReg URL is accessed directly.(*PA*)
+- The subdomain tooltip now informs the user that it must match the subdomain part of the base URL provided. (*CZ*)
 
 ## This release includes code contributions from
 ### ByWater Solutions
diff --git a/code/web/sys/LibraryLocation/Library.php b/code/web/sys/LibraryLocation/Library.php
index 260b0714a8..d2063c7b82 100644
--- a/code/web/sys/LibraryLocation/Library.php
+++ b/code/web/sys/LibraryLocation/Library.php
@@ -952,7 +952,7 @@ static function getObjectStructure($context = ''): array {
 				'property' => 'subdomain',
 				'type' => 'text',
 				'label' => 'Subdomain',
-				'description' => 'A unique id to identify the library within the system',
+				'description' => 'A unique id to identify the library within the system. This much match the base URL subdomain used.',
 				'uniqueProperty' => true,
 				'forcesReindex' => true,
 				'required' => true,