diff --git a/netclass.cc b/netclass.cc
index 3365a8949..99ad5d68a 100644
--- a/netclass.cc
+++ b/netclass.cc
@@ -195,3 +195,14 @@ const NetExpr* netclass_t::get_parameter(Design *des, perm_string name,
 {
       return class_scope_->get_parameter(des, name, par_type);
 }
+
+bool netclass_t::test_compatibility(ivl_type_t that) const
+{
+      for (const netclass_t *class_type = dynamic_cast<const netclass_t *>(that);
+	    class_type; class_type = class_type->get_super()) {
+	    if (class_type == this)
+		  return true;
+      }
+
+      return false;
+}
diff --git a/netclass.h b/netclass.h
index 0c598fe32..a34487e9b 100644
--- a/netclass.h
+++ b/netclass.h
@@ -119,6 +119,9 @@ class netclass_t : public ivl_type_s {
       void set_virtual(bool virtual_class) { virtual_class_ = virtual_class; }
       bool is_virtual() const { return virtual_class_; }
 
+    protected:
+      bool test_compatibility(ivl_type_t that) const;
+
     private:
       perm_string name_;
 	// If this is derived from another base class, point to it