diff --git a/specification/e-referrals-service-api.yaml b/specification/e-referrals-service-api.yaml
index bd06e4e23..da7daafb1 100644
--- a/specification/e-referrals-service-api.yaml
+++ b/specification/e-referrals-service-api.yaml
@@ -253,6 +253,8 @@ info:
   license:
     name: MIT
 servers:
+  - url: 'https://internal-dev-sandbox.api.service.nhs.uk/referrals-pr-597/FHIR'
+    description: Sandbox environment.
   - url: 'https://sandbox.api.service.nhs.uk/referrals/FHIR'
     description: Sandbox environment.
   - url: 'https://int.api.service.nhs.uk/referrals/FHIR'