diff --git a/src/controllers/categories.js b/src/controllers/categories.js
index 80bf87907a..53ad658966 100644
--- a/src/controllers/categories.js
+++ b/src/controllers/categories.js
@@ -162,7 +162,7 @@ categoriesController.get = function(req, res, next) {
 		page = parseInt(req.query.page, 10) || 1,
 		userPrivileges;
 
-	if (req.params.topic_index && !utils.isNumber(req.params.topic_index)) {
+	if ((req.params.topic_index && !utils.isNumber(req.params.topic_index)) || !utils.isNumber(cid)) {
 		return helpers.notFound(req, res);
 	}
 
diff --git a/src/controllers/topics.js b/src/controllers/topics.js
index 3f96682c31..b65b3b997a 100644
--- a/src/controllers/topics.js
+++ b/src/controllers/topics.js
@@ -21,7 +21,7 @@ topicsController.get = function(req, res, next) {
 		sort = req.query.sort,
 		userPrivileges;
 
-	if (req.params.post_index && !utils.isNumber(req.params.post_index)) {
+	if ((req.params.post_index && !utils.isNumber(req.params.post_index)) || !utils.isNumber(tid)) {
 		return helpers.notFound(req, res);
 	}