diff --git a/src/mergerfs_webui.cpp b/src/mergerfs_webui.cpp
index 81379d67..f5c1dadf 100644
--- a/src/mergerfs_webui.cpp
+++ b/src/mergerfs_webui.cpp
@@ -187,6 +187,12 @@ _get_kvs(const httplib::Request &req_,
   std::string mount;
   std::map<std::string,std::string> kvs;
 
+  if(not req_.has_param("mount"))
+    {
+      res_.status = 400;
+      res_.set_content("mount param not set", "text/plain");
+    }
+
   mount = req_.get_param_value("mount");
 
   mergerfs::api::get_kvs(mount,&kvs);