diff --git a/src/UserData/UserDataScriptType.hpp b/src/UserData/UserDataScriptType.hpp
index 55651af..45cd35b 100644
--- a/src/UserData/UserDataScriptType.hpp
+++ b/src/UserData/UserDataScriptType.hpp
@@ -90,7 +90,7 @@ namespace Porygon::UserData {
 
         [[nodiscard]] bool CanSetIndexValue(Utilities::HashedString indexer, shared_ptr<const ScriptType> val) const override {
             auto ud = _userData->Get();
-            if (ud->ContainsField(indexer.GetHash()))
+            if (!ud->ContainsField(indexer.GetHash()))
                 return false;
             auto field = _userData->Get()->GetField(indexer.GetHash());
             return (val->CastableTo(field->GetType(), false) != CastResult::InvalidCast);