diff --git a/public/src/forum/category.js b/public/src/forum/category.js
index e71dfc185f..1fa4d359ec 100644
--- a/public/src/forum/category.js
+++ b/public/src/forum/category.js
@@ -307,7 +307,7 @@ define(['composer', 'forum/pagination', 'share', 'navigator', 'forum/categoryToo
 			return;
 		}
 
-		if(after === 0 && $('#topics-container li.category-item[data-index="0"]').length) {
+		if(!utils.isNumber(after) || (after === 0 && $('#topics-container li.category-item[data-index="0"]').length)) {
 			return;
 		}
 
diff --git a/public/src/forum/topic.js b/public/src/forum/topic.js
index 50954debfa..bae43ba3c1 100644
--- a/public/src/forum/topic.js
+++ b/public/src/forum/topic.js
@@ -744,7 +744,7 @@ define(['forum/pagination', 'forum/topic/threadTools', 'forum/topic/postTools',
 			return;
 		}
 
-		if(after === 0 && $('#post-container li.post-row[data-index="0"]').length) {
+		if (!utils.isNumber(after) || (after === 0 && $('#post-container li.post-row[data-index="0"]').length)) {
 			return;
 		}