diff --git a/config/environments/production.rb b/config/environments/production.rb
index d3a7697d4..7720f212b 100644
--- a/config/environments/production.rb
+++ b/config/environments/production.rb
@@ -80,7 +80,7 @@
 
   # Enable DNS rebinding protection and other `Host` header attacks.
   config.hosts = [
-    /transition\..*gov.uk?/,
+    /transition\..*\.gov.uk$/,
   ]
 
   # Skip DNS rebinding protection for the default health check endpoint.