diff --git a/administrator/components/com_patchtester/PatchTester/View/Pulls/PullsHtmlView.php b/administrator/components/com_patchtester/PatchTester/View/Pulls/PullsHtmlView.php
index a731d14..6b16001 100644
--- a/administrator/components/com_patchtester/PatchTester/View/Pulls/PullsHtmlView.php
+++ b/administrator/components/com_patchtester/PatchTester/View/Pulls/PullsHtmlView.php
@@ -113,6 +113,12 @@ class PullsHtmlView extends DefaultHtmlView
 		// Make text strings available in the JavaScript API
 		Text::script('COM_PATCHTESTER_CONFIRM_RESET');
 
+		// Set a warning on 4.0 branch
+		if (version_compare(JVERSION, '4.0', 'ge'))
+		{
+			Factory::getApplication()->enqueueMessage(Text::_('COM_PATCHTESTER_40_WARNING'), 'warning');
+		}
+
 		return parent::render();
 	}
 
diff --git a/administrator/components/com_patchtester/language/en-GB/com_patchtester.ini b/administrator/components/com_patchtester/language/en-GB/com_patchtester.ini
index b5d0fa2..df40527 100644
--- a/administrator/components/com_patchtester/language/en-GB/com_patchtester.ini
+++ b/administrator/components/com_patchtester/language/en-GB/com_patchtester.ini
@@ -4,6 +4,7 @@
 ; Note : All ini files need to be saved as UTF-8
 
 COM_PATCHTESTER="Joomla! Patch Tester"
+COM_PATCHTESTER_40_WARNING="While Joomla! 4.0 is in development, using the patch tester is considered experimental since breaking changes may be merged into Joomla, including the code contained in a patch."
 COM_PATCHTESTER_API_LIMIT_ACTION="The GitHub API rate limit has been reached for this resource, could not connect to GitHub to perform the requested action. The rate limit will reset at %s"
 COM_PATCHTESTER_API_LIMIT_LIST="The GitHub API rate limit has been reached for this resource, could not connect to GitHub for updated data. The rate limit will reset at %s"
 COM_PATCHTESTER_APPLIED="Applied"