diff --git a/compiler/cpp/src/parse/t_scope.h b/compiler/cpp/src/parse/t_scope.h
index 585b910..91ec312 100644
--- a/compiler/cpp/src/parse/t_scope.h
+++ b/compiler/cpp/src/parse/t_scope.h
@@ -60,7 +60,12 @@
   }
 
   void add_constant(std::string name, t_const* constant) {
-    constants_[name] = constant;
+    if (constants_.find(name) != constants_.end()) {
+      throw "Enum " + name + " is already defined!";
+    } else {
+      constants_[name] = constant;
+    }
+		   
   }
 
   t_const* get_constant(std::string name) {