TypeScript Error TS2416 — Property Not Assignable to Same Property in Base Type

What Does This Error Mean?

A class method or property you overrode is not compatible with the base class version. TypeScript enforces the Liskov Substitution Principle — subclasses must be usable wherever the base class is. Fix the overriding method's signature to match or extend the base type.

Affected Models

TypeScript 5.x
TypeScript 4.x
React + TypeScript
Node.js + TypeScript

Common Causes

Overriding a method with a narrower parameter type than the base class method
Returning a type in an override that is not compatible with the base return type
Implementing an interface method with a signature that does not match the interface
Changing a method to accept fewer arguments than the base class method
Using a completely different type in an overridden property

How to Fix It

Find the base class or interface method that your override is conflicting with.

Hold Ctrl and click the method name in VS Code to jump to the base definition.
Make your overriding method's parameter types at least as broad as the base type.

If the base accepts Animal, your override must also accept Animal — not a narrower subtype like Dog.
Make your return type at least as specific as the base type.

If the base returns Animal, your override can return Dog (a subtype). It cannot return a completely different type.
Use a union type in the override to accept both the base type and any additional types you need.

Example: if base takes string, override can take string | number to be broader.
If the base class design is wrong, refactor the base method to use a more flexible type from the start.

Using a generic type parameter on the base class method is a clean solution when subclasses genuinely differ.

When to Call a Professional

TS2416 is a design-level type error. You can fix it yourself by aligning the override signature. If the class hierarchy is deeply complex, a code review helps ensure the fix does not break callers.

Frequently Asked Questions

What is the Liskov Substitution Principle and why does TypeScript enforce it?

It says a subclass must be usable anywhere the base class is used. If an override narrows types, code that works with the base class may break when given a subclass. TypeScript catches this at compile time to prevent subtle runtime bugs.

Can I use @ts-ignore to bypass this error?

You can, but it hides a real design problem. Code that passes a base class instance to a function will fail at runtime if the subclass override cannot handle the same inputs. Fix the signatures instead.

What is the override keyword and should I use it?

The override keyword (TypeScript 4.3+) marks that a method intentionally overrides a base class method. TypeScript then errors if the base class method is removed — catching accidental orphaned overrides. It is good practice to use override on every method you intend to replace.