diff --git a/src/apps.js b/src/apps.js
index 0b91fd5f4..70ec69122 100644
--- a/src/apps.js
+++ b/src/apps.js
@@ -280,7 +280,7 @@ function validateSecondaryDomains(secondaryDomains, manifest) {
     }
 
     for (const envName in secondaryDomains) {
-        if (!(envName in httpPorts)) return new BoxError(BoxError.BAD_FIELD, `Invalid secondaryDomain in ${envName}`);
+        if (!(envName in httpPorts)) return new BoxError(BoxError.BAD_FIELD, `secondaryDomain ${envName} is not listed in manifest`);
     }
 
     return null;