diff --git a/src/headers/parsing/Parser.hpp b/src/headers/parsing/Parser.hpp
index 7a7448b..3020ad5 100644
--- a/src/headers/parsing/Parser.hpp
+++ b/src/headers/parsing/Parser.hpp
@@ -149,19 +149,21 @@ namespace Parser {
             } catch (const NamedIdentifier<true>::identifier_reserved_exception&) {
                 parsingError(current, " is a reserved identifier", true);
             }
-            const auto& last = parseTree.cend() - 1;
-            const type_info& lastId = last->get()->getId();
-            const auto* last_identifier = dynamic_cast<NamedIdentifier<true>*>(last->get());
-            if (last_identifier != nullptr) {
-                if (lastId != typeid(Define) and
-                    any_of(parseTree.cbegin(), last, [&last_identifier](const component_ptr& pointer){
-                        try {
-                            return dynamic_cast<NamedIdentifier<true>&>(*pointer).name == last_identifier->name;
-                        } catch (const bad_cast&) {
-                            return false;
-                        }
-                    }))
-                { parsingError(current, " has already been defined previously", true); }
+            if (not parseTree.empty())  {
+                const auto& last = parseTree.cend() - 1;
+                const type_info& lastId = last->get()->getId();
+                const auto* last_identifier = dynamic_cast<NamedIdentifier<true>*>(last->get());
+                if (last_identifier != nullptr) {
+                    if (lastId != typeid(Define) and
+                        any_of(parseTree.cbegin(), last, [&last_identifier](const component_ptr& pointer){
+                            try {
+                                return dynamic_cast<NamedIdentifier<true>&>(*pointer).name == last_identifier->name;
+                            } catch (const bad_cast&) {
+                                return false;
+                            }
+                        }))
+                    { parsingError(current, " has already been defined previously", true); }
+                }
             }
         }
         return parseTree;