diff --git a/src/data/abilities/ability.ts b/src/data/abilities/ability.ts
index 0c259f3f639..d8743a0effe 100644
--- a/src/data/abilities/ability.ts
+++ b/src/data/abilities/ability.ts
@@ -86,7 +86,7 @@ export class Ability implements Localizable {
   public name: string;
   public description: string;
   public generation: number;
-  public postSummonPriority: number;
+  public readonly postSummonPriority: number;
   public isBypassFaint: boolean;
   public isIgnorable: boolean;
   public isSuppressable = true;