diff --git a/node_modules/@lit/reactive-element/reactive-element.d.ts b/node_modules/@lit/reactive-element/reactive-element.d.ts
index c5c21f4ff4a1a..2fe682da147d3 100644
--- a/node_modules/@lit/reactive-element/reactive-element.d.ts
+++ b/node_modules/@lit/reactive-element/reactive-element.d.ts
@@ -57,7 +57,9 @@ type AttributeConverter<Type = unknown, TypeHint = unknown> = ComplexAttributeCo
 /**
  * Defines options for a property accessor.
  */
-export interface PropertyDeclaration<Type = unknown, TypeHint = unknown> {
+// Chromium patch to only allow one of [String, Number, Boolean, Array, Object]
+// in 'type' fields, since these are the only actual valid values.
+export interface PropertyDeclaration<Type = unknown, TypeHint = typeof String|typeof Number|typeof Boolean|typeof Array|typeof Object> {
     /**
      * When set to `true`, indicates the property is internal private state. The
      * property should not be set by users. When using TypeScript, this property
@@ -78,8 +80,10 @@ export interface PropertyDeclaration<Type = unknown, TypeHint = unknown> {
      * Indicates the type of the property. This is used only as a hint for the
      * `converter` to determine how to convert the attribute
      * to/from a property.
+     * Chromium patch to make this property required, since the type is
+     * validated against the declared TS type.
      */
-    readonly type?: TypeHint;
+    readonly type: TypeHint;
     /**
      * Indicates how to convert the attribute to/from a property. If this value
      * is a function, it is used to convert the attribute value a the property