diff --git a/src/headers/parsing/ParseComponents.hpp b/src/headers/parsing/ParseComponents.hpp
index 33c8426..9d708c0 100644
--- a/src/headers/parsing/ParseComponents.hpp
+++ b/src/headers/parsing/ParseComponents.hpp
@@ -81,8 +81,8 @@ public:
     }
     IS(StandardComponents::NamedIdentifier)
     optional<reference_wrapper<T>> findReferenceByName(const string& name) const {
-        auto identifiers = findById<T>();
-        for (const auto& identifier: identifiers) {
+        const vector<T*> identifiers = findById<T>();
+        for (T* identifier: identifiers) {
             if (identifier->getId() == typeid(T) && identifier->name == name) {
                 return make_optional(ref(static_cast<T&>(*identifier)));
             }
diff --git a/src/headers/parsing/Parser.hpp b/src/headers/parsing/Parser.hpp
index fb9bc0a..f93551d 100644
--- a/src/headers/parsing/Parser.hpp
+++ b/src/headers/parsing/Parser.hpp
@@ -36,6 +36,10 @@ namespace Parser {
                     } else {
                         bool isFinalDefine = nextAre({TAG, DEFINE});
                         if (isFinalDefine || next.toktype == DEFINE) {
+                            const optional previousDefinition = parseTree.findReferenceByName<Define>(current.toktext);
+                            if (previousDefinition.has_value() && previousDefinition.value().get().final) {
+                                throw ParsingException(current.toktext + " cannot be redefined as it is final", current.line);
+                            }
                             parseTree << Define(isFinalDefine, current.toktext);
                             i += 1 + isFinalDefine;
                         } else {