diff --git a/src/@types/illusion-data.ts b/src/@types/illusion-data.ts
index b152e3fdf59..5bf86d23ac2 100644
--- a/src/@types/illusion-data.ts
+++ b/src/@types/illusion-data.ts
@@ -11,7 +11,7 @@ export interface IllusionData {
   /** The name of pokemon featured in the illusion */
   name: string;
   /** The nickname of the pokemon featured in the illusion */
-  nickname: string;
+  nickname?: string;
   /** Whether the pokemon featured in the illusion is shiny or not */
   shiny: boolean;
   /** The variant of the pokemon featured in the illusion */
diff --git a/src/field/pokemon.ts b/src/field/pokemon.ts
index fd04c007e1b..7aecc0c8e75 100644
--- a/src/field/pokemon.ts
+++ b/src/field/pokemon.ts
@@ -213,7 +213,11 @@ export abstract class Pokemon extends Phaser.GameObjects.Container {
    * TODO: Stop treating this like a unique ID and stop treating 0 as no pokemon
    */
   public id: number;
-  public nickname: string;
+  /**
+   * The Pokemon's current nickname, or `undefined` if it currently lacks one.
+   * If omitted, references to this should refer to the default name for this Pokemon's species.
+   */
+  public nickname?: string;
   public species: PokemonSpecies;
   public formIndex: number;
   public abilityIndex: number;
@@ -443,7 +447,7 @@ export abstract class Pokemon extends Phaser.GameObjects.Container {
   getNameToRender(useIllusion = true) {
     const illusion = this.summonData.illusion;
     const name = useIllusion ? (illusion?.name ?? this.name) : this.name;
-    const nickname: string = useIllusion ? (illusion?.nickname ?? this.nickname) : this.nickname;
+    const nickname: string | undefined = useIllusion ? illusion?.nickname : this.nickname;
     try {
       if (nickname) {
         return decodeURIComponent(escape(atob(nickname))); // TODO: Remove `atob` and `escape`... eventually...