diff --git a/src/ast/identifier_expression.h b/src/ast/identifier_expression.h
index 4c6ac31..b13fb0e 100644
--- a/src/ast/identifier_expression.h
+++ b/src/ast/identifier_expression.h
@@ -26,7 +26,7 @@
 namespace ast {
 
 /// An identifier expression
-class IdentifierExpression : public Expression {
+class IdentifierExpression : public Castable<IdentifierExpression, Expression> {
  public:
   /// Constructor
   /// @param name the name