diff --git a/src/battle-scene.ts b/src/battle-scene.ts
index 4269edecfaf..c0b6e2ba91e 100644
--- a/src/battle-scene.ts
+++ b/src/battle-scene.ts
@@ -1115,27 +1115,11 @@ export default class BattleScene extends SceneBase {
     //this.pushPhase(new TrainerMessageTestPhase(this, TrainerType.RIVAL, TrainerType.RIVAL_2, TrainerType.RIVAL_3, TrainerType.RIVAL_4, TrainerType.RIVAL_5, TrainerType.RIVAL_6));
 
     if (!waveIndex && lastBattle) {
-      let isNewBiome = !(lastBattle.waveIndex % 10) || ((this.gameMode.hasShortBiomes || this.gameMode.isDaily) && (lastBattle.waveIndex % 50) === 49);
-      if (!isNewBiome && this.gameMode.hasShortBiomes && (lastBattle.waveIndex % 10) < 9) {
-        let w = lastBattle.waveIndex - ((lastBattle.waveIndex % 10) - 1);
-        let biomeWaves = 1;
-        while (w < lastBattle.waveIndex) {
-          let wasNewBiome = false;
-          this.executeWithSeedOffset(() => {
-            wasNewBiome = !Utils.randSeedInt(6 - biomeWaves);
-          }, w << 4);
-          if (wasNewBiome) {
-            biomeWaves = 1;
-          } else {
-            biomeWaves++;
-          }
-          w++;
-        }
-
-        this.executeWithSeedOffset(() => {
-          isNewBiome = !Utils.randSeedInt(6 - biomeWaves);
-        }, lastBattle.waveIndex << 4);
-      }
+      const isWaveIndexMultipleOfTen = !(lastBattle.waveIndex % 10);
+      const isEndlessOrDaily = this.gameMode.hasShortBiomes || this.gameMode.isDaily;
+      const isEndlessFifthWave = this.gameMode.hasShortBiomes && (lastBattle.waveIndex % 5) === 0;
+      const isWaveIndexMultipleOfFiftyMinusOne = (lastBattle.waveIndex % 50) === 49;
+      const isNewBiome = isWaveIndexMultipleOfTen || isEndlessFifthWave || (isEndlessOrDaily && isWaveIndexMultipleOfFiftyMinusOne);
       const resetArenaState = isNewBiome || this.currentBattle.battleType === BattleType.TRAINER || this.currentBattle.battleSpec === BattleSpec.FINAL_BOSS;
       this.getEnemyParty().forEach(enemyPokemon => enemyPokemon.destroy());
       this.trySpreadPokerus();
diff --git a/src/modifier/modifier.ts b/src/modifier/modifier.ts
index 6ff2d3c9718..c6871353a7d 100644
--- a/src/modifier/modifier.ts
+++ b/src/modifier/modifier.ts
@@ -1818,7 +1818,7 @@ export class PokemonExpBoosterModifier extends PokemonHeldItemModifier {
   }
 
   apply(args: any[]): boolean {
-    (args[1] as Utils.NumberHolder).value += (this.getStackCount() * this.boostMultiplier);
+    (args[1] as Utils.NumberHolder).value = Math.floor((args[1] as Utils.NumberHolder).value * (1 + (this.getStackCount() * this.boostMultiplier)));
 
     return true;
   }
diff --git a/src/phases.ts b/src/phases.ts
index ac6da0db148..39cbbd5ff8b 100644
--- a/src/phases.ts
+++ b/src/phases.ts
@@ -3988,9 +3988,7 @@ export class VictoryPhase extends PokemonPhase {
           expMultiplier = Overrides.XP_MULTIPLIER_OVERRIDE;
         }
         const pokemonExp = new Utils.NumberHolder(expValue * expMultiplier);
-        const modifierBonusExp = new Utils.NumberHolder(1);
-        this.scene.applyModifiers(PokemonExpBoosterModifier, true, partyMember, modifierBonusExp);
-        pokemonExp.value *= modifierBonusExp.value;
+        this.scene.applyModifiers(PokemonExpBoosterModifier, true, partyMember, pokemonExp);
         partyMemberExp.push(Math.floor(pokemonExp.value));
       }
 
diff --git a/src/test/items/exp_booster.test.ts b/src/test/items/exp_booster.test.ts
index 3348304b2e7..2b700c92086 100644
--- a/src/test/items/exp_booster.test.ts
+++ b/src/test/items/exp_booster.test.ts
@@ -27,13 +27,14 @@ describe("EXP Modifier Items", () => {
     game.override.battleType("single");
   });
 
-  it("EXP booster items stack additively", async() => {
-    game.override.startingHeldItems([{name: "LUCKY_EGG"}, {name: "GOLDEN_EGG"}]);
+  it("EXP booster items stack multiplicatively", async() => {
+    game.override.startingHeldItems([{name: "LUCKY_EGG", count: 3}, {name: "GOLDEN_EGG"}]);
     await game.startBattle();
 
     const partyMember = game.scene.getPlayerPokemon()!;
-    const modifierBonusExp = new Utils.NumberHolder(1);
-    partyMember.scene.applyModifiers(PokemonExpBoosterModifier, true, partyMember, modifierBonusExp);
-    expect(modifierBonusExp.value).toBe(2.4);
+    partyMember.exp = 100;
+    const expHolder = new Utils.NumberHolder(partyMember.exp);
+    partyMember.scene.applyModifiers(PokemonExpBoosterModifier, true, partyMember, expHolder);
+    expect(expHolder.value).toBe(440);
   }, 20000);
 });
diff --git a/vite.config.ts b/vite.config.ts
index f5c95aa56bd..4bd013bff2e 100644
--- a/vite.config.ts
+++ b/vite.config.ts
@@ -20,7 +20,8 @@ export const defaultConfig = {
 			}
 			warn(warning);
 		},
-	}
+	},
+	appType: "mpa",
 };