diff --git a/src/pvxs/data.h b/src/pvxs/data.h
index f4bdeaf..114552f 100644
--- a/src/pvxs/data.h
+++ b/src/pvxs/data.h
@@ -243,6 +243,10 @@ private:
 public:
     struct Helper;
 
+    //! Empty/invalid Member
+    inline
+    Member() :code(TypeCode::Null) {}
+
     //! Member for non-Compund
     //! @pre code.kind()!=Kind::Compound
     inline
diff --git a/src/type.cpp b/src/type.cpp
index 2e1aac6..540c542 100644
--- a/src/type.cpp
+++ b/src/type.cpp
@@ -126,6 +126,8 @@ void Member::Helper::node_validate(const Member* parent, const std::string& id,
 {
     if(!id.empty() && code.scalarOf()!=TypeCode::Struct && code.scalarOf()!=TypeCode::Union)
         throw std::logic_error("Only Struct or Union may have an ID");
+    else if(!code.valid())
+        throw std::logic_error("Invalid TypeCode");
     if(parent) {
         auto c = parent->code.scalarOf();
         if(c!=TypeCode::Struct && c!=TypeCode::Union)