Design-time code (property editors, component editors, IDE wizards, etc) are simply not allowed in runtime executables, period. So, your home-grown component needs to be implemented in a runtime-only package, and any code that relies on the DesignIDE package needs to be implemented in a designtime-only package that "requires" the runtime-only package. Your component should have no concept of design-time whatsoever (outside of things like the csDesigning flag in its ComponentState property, the CM_DESIGNHITTEST message, etc). If that is not the case, then the component is not architectured properly.