diff --git a/picard/webservice/api_helpers.py b/picard/webservice/api_helpers.py
index d31f9b710..fb96df92c 100644
--- a/picard/webservice/api_helpers.py
+++ b/picard/webservice/api_helpers.py
@@ -239,10 +239,9 @@ class MBAPIHelper(APIHelper):
         return self.get_collection(None, handler)
 
     @staticmethod
-    def _collection_request(collection_id, releases):
-        while releases:
-            ids = ";".join(releases if len(releases) <= 400 else releases[:400])
-            releases = releases[400:]
+    def _collection_request(collection_id, releases, batchsize=400):
+        for i in range(0, len(releases), batchsize):
+            ids = ";".join(releases[i:i+batchsize])
             yield ("collection", collection_id, "releases", ids)
 
     @staticmethod
diff --git a/test/test_api_helpers.py b/test/test_api_helpers.py
index f130a51b3..0c88648a4 100644
--- a/test/test_api_helpers.py
+++ b/test/test_api_helpers.py
@@ -179,3 +179,15 @@ class MBAPITest(PicardTestCase):
             '</recording-list>'
             '</metadata>'
         )
+
+    def test_collection_request(self):
+        releases = tuple("r"+str(i) for i in range(13))
+        generator = self.api._collection_request("test", releases, batchsize=5)
+        batch = next(generator)
+        self.assertEqual(batch, ('collection', 'test', 'releases', 'r0;r1;r2;r3;r4'))
+        batch = next(generator)
+        self.assertEqual(batch, ('collection', 'test', 'releases', 'r5;r6;r7;r8;r9'))
+        batch = next(generator)
+        self.assertEqual(batch, ('collection', 'test', 'releases', 'r10;r11;r12'))
+        with self.assertRaises(StopIteration):
+            next(generator)