diff --git a/src/storage/caas.js b/src/storage/caas.js
index f0e6e40ed..6e88f0d1e 100644
--- a/src/storage/caas.js
+++ b/src/storage/caas.js
@@ -65,7 +65,7 @@ function getAppBackupDetails(apiConfig, appId, dataId, configId, callback) {
     assert.strictEqual(typeof apiConfig, 'object');
     assert.strictEqual(typeof appId, 'string');
     assert.strictEqual(typeof dataId, 'string');
-    assert.strictEqual(typeof configId, '');
+    assert.strictEqual(typeof configId, 'string');
     assert.strictEqual(typeof callback, 'function');
 
     getBackupCredentials(apiConfig, function (error, result) {