diff --git a/src/data/move.ts b/src/data/move.ts
index 40e8afd91ae..9e3c9a41a05 100644
--- a/src/data/move.ts
+++ b/src/data/move.ts
@@ -1951,7 +1951,7 @@ export class ConditionalHealAttr extends VariablePowerAttr {
   private callback: (user: Pokemon, target: Pokemon, move: Move) => boolean;
   private healRatio: number;
 
-  constructor(callback: (user: Pokemon, target: Pokemon, move: Move) => boolean, healRatio?: number) {
+  constructor(callback: (user: Pokemon, target: Pokemon, move: Move) => boolean, healRatio: number = 0.5) {
     super();
     this.callback = callback;
     this.healRatio = healRatio;