diff --git a/src/torque/types.cc b/src/torque/types.cc
index bdc4d89273..061919111d 100644
--- a/src/torque/types.cc
+++ b/src/torque/types.cc
@@ -289,6 +289,8 @@ std::string StructType::ToExplicitString() const {
   return result.str();
 }
 
+constexpr ClassFlags ClassType::kInternalFlags;
+
 ClassType::ClassType(const Type* parent, Namespace* nspace,
                      const std::string& name, ClassFlags flags,
                      const std::string& generates, const ClassDeclaration* decl,