diff --git a/packages/agoric-cli/src/main-publish.js b/packages/agoric-cli/src/main-publish.js
index 8c51378cb3b9..4485f45f8c7d 100644
--- a/packages/agoric-cli/src/main-publish.js
+++ b/packages/agoric-cli/src/main-publish.js
@@ -47,7 +47,9 @@ const publishMain = async (progname, rawArgs, powers, opts) => {
     });
     const publishBundle = makeBundlePublisher({
       getDefaultConnection() {
-        throw new Error(``);
+        throw new Error(
+          'Invariant: publishBundle will never call getDefaultConnection because we provide an explicit connectionSpec',
+        );
       },
       publishBundleCosmos,
     });