diff --git a/src/logic/scripting/lua/libs/libgui.cpp b/src/logic/scripting/lua/libs/libgui.cpp
index af317f94..68327c8e 100644
--- a/src/logic/scripting/lua/libs/libgui.cpp
+++ b/src/logic/scripting/lua/libs/libgui.cpp
@@ -490,6 +490,12 @@ static int p_get_scroll(UINode* node, lua::State* L) {
 }
 
 static int l_gui_getattr(lua::State* L) {
+    if (!lua::isstring(L, 1)) {
+        throw std::runtime_error("document name is not a string");
+    }
+    if (!lua::isstring(L, 2)) {
+        throw std::runtime_error("element id is not a string");
+    }
     auto docname = lua::require_string(L, 1);
     auto element = lua::require_string(L, 2);
     if (lua::isnumber(L, 3)) {
@@ -507,6 +513,9 @@ static int l_gui_getattr(lua::State* L) {
         const auto& id = request_node_id(DocumentNode {docnode.document, node});
         return push_document_node(L, id);
     }
+    if (!lua::isstring(L, 3)) {
+        throw std::runtime_error("attribute name is not a string");
+    }
     auto attr = lua::require_string(L, 3);
 
     static const std::unordered_map<
@@ -755,6 +764,15 @@ static int p_set_scroll(UINode* node, lua::State* L, int idx) {
 }
 
 static int l_gui_setattr(lua::State* L) {
+    if (!lua::isstring(L, 1)) {
+        throw std::runtime_error("document name is not a string");
+    }
+    if (!lua::isstring(L, 2)) {
+        throw std::runtime_error("element id is not a string");
+    }
+    if (!lua::isstring(L, 3)) {
+        throw std::runtime_error("attribute name is not a string");
+    }
     auto docname = lua::require_string(L, 1);
     auto element = lua::require_string(L, 2);
     auto attr = lua::require_string(L, 3);