diff --git a/server/core/BookUpdateChecker/BUCClient.js b/server/core/BookUpdateChecker/BUCClient.js
index 7ea33e83..30fea23e 100644
--- a/server/core/BookUpdateChecker/BUCClient.js
+++ b/server/core/BookUpdateChecker/BUCClient.js
@@ -177,8 +177,10 @@ class BUCClient {
 
                             const ids = new Set();
                             let id = iter.next();
-                            while (!id.done && ids.size < 1000) {
+                            while (!id.done) {
                                 ids.add(id.value);
+                                if (ids.size >= 1000)
+                                    break;
                                 id = iter.next();
                             }
 
diff --git a/server/core/BookUpdateChecker/BUCServer.js b/server/core/BookUpdateChecker/BUCServer.js
index 820c44aa..d78c15b0 100644
--- a/server/core/BookUpdateChecker/BUCServer.js
+++ b/server/core/BookUpdateChecker/BUCServer.js
@@ -78,8 +78,10 @@ class BUCServer {
 
                     const ids = new Set();
                     let id = iter.next();
-                    while (!id.done && ids.size < 100) {
+                    while (!id.done) {
                         ids.add(id.value);
+                        if (ids.size >= 100)
+                            break;
                         id = iter.next();
                     }