diff --git a/schema.d.ts b/schema.d.ts
index 2819de6..088cfb2 100644
--- a/schema.d.ts
+++ b/schema.d.ts
@@ -299,6 +299,11 @@ export interface Attribute {
    * If the value is a string, it's the reason for the deprecation.
    */
   deprecated?: boolean|string;
+
+  /**
+   * Whether the attribute is read-only.
+   */
+  readonly?: boolean;
 }
 
 export interface Event {
@@ -554,6 +559,11 @@ export interface PropertyLike {
    * If the value is a string, it's the reason for the deprecation.
    */
   deprecated?: boolean|string;
+
+  /**
+   * Whether the property is read-only.
+   */
+  readonly?: boolean;
 }
 
 export interface ClassField extends PropertyLike {