diff --git a/src/syncer.js b/src/syncer.js
index 7acd6e4dc..b9d728c89 100644
--- a/src/syncer.js
+++ b/src/syncer.js
@@ -163,7 +163,7 @@ async function sync(dataLayout, cacheFile) {
 }
 
 async function finalize(integrityMap, cacheFile) {
-    assert(util.types.isMap(integrityMap));
+    assert(util.types.isMap(integrityMap), 'integrityMap is not a Map');
     assert.strictEqual(typeof cacheFile, 'string');
 
     const newCacheFile = `${cacheFile}.new`, tempCacheFile = `${cacheFile}.tmp`;
diff --git a/src/test/syncer-test.js b/src/test/syncer-test.js
index c76fb704a..c8db84b7a 100644
--- a/src/test/syncer-test.js
+++ b/src/test/syncer-test.js
@@ -24,9 +24,9 @@ describe('Syncer', function () {
     });
 
     async function getChanges(dataLayout) {
-        const changes = await syncer.sync(dataLayout, gCacheFile);
-        syncer.finalize(gCacheFile);
-        return changes.delQueue.concat(changes.addQueue);
+        const { delQueue, addQueue, integrityMap } = await syncer.sync(dataLayout, gCacheFile);
+        await syncer.finalize(integrityMap, gCacheFile);
+        return delQueue.concat(addQueue);
     }
 
     it('missing cache - removes remote dir', async function () {