diff --git a/src/modifier/modifier.ts b/src/modifier/modifier.ts
index 980a401b305..09614f01027 100644
--- a/src/modifier/modifier.ts
+++ b/src/modifier/modifier.ts
@@ -1041,13 +1041,13 @@ export class ShinyRateBoosterModifier extends PersistentModifier {
   }
 
   apply(args: any[]): boolean {
-    (args[0] as Utils.IntegerHolder).value = Math.pow((args[0] as Utils.IntegerHolder).value * 0.5, this.getStackCount() + 1);
+    (args[0] as Utils.IntegerHolder).value = Math.floor(Math.pow((args[0] as Utils.IntegerHolder).value * 0.5, Math.sqrt(this.getStackCount()) + 1));
 
     return true;
   }
 
   getMaxStackCount(): integer {
-    return 4;
+    return 5;
   }
 }