diff --git a/include/battle_util.h b/include/battle_util.h
index 96ffc2fa16c0..b5ba5249ea2c 100644
--- a/include/battle_util.h
+++ b/include/battle_util.h
@@ -212,6 +212,8 @@ bool8 IsMoveAffectedByParentalBond(u16 move, u8 battlerId);
 void CopyMonLevelAndBaseStatsToBattleMon(u32 battler, struct Pokemon *mon);
 void CopyMonAbilityAndTypesToBattleMon(u32 battler, struct Pokemon *mon);
 void RecalcBattlerStats(u32 battler, struct Pokemon *mon);
+void MulModifier(u16 *modifier, u16 val);
+
 // Ability checks
 bool32 IsRolePlayBannedAbilityAtk(u16 ability);
 bool32 IsRolePlayBannedAbility(u16 ability);
diff --git a/src/battle_ai_switch_items.c b/src/battle_ai_switch_items.c
index d7fd062ba212..cd9c173a9573 100644
--- a/src/battle_ai_switch_items.c
+++ b/src/battle_ai_switch_items.c
@@ -822,7 +822,7 @@ static u32 GetBestMonTypeMatchup(struct Pokemon *party, int firstId, int lastId,
 
     while (bits != 0x3F) // All mons were checked.
     {
-        u32 bestResist = UQ_4_12(1.0);
+        u16 bestResist = UQ_4_12(1.0);
         int bestMonId = PARTY_SIZE;
         // Find the mon whose type is the most suitable defensively.
         for (i = firstId; i < lastId; i++)
@@ -830,21 +830,21 @@ static u32 GetBestMonTypeMatchup(struct Pokemon *party, int firstId, int lastId,
             if (!(gBitTable[i] & invalidMons) && !(gBitTable[i] & bits))
             {
                 u16 species = GetMonData(&party[i], MON_DATA_SPECIES);
-                u32 typeEffectiveness = UQ_4_12(1.0);
+                u16 typeEffectiveness = UQ_4_12(1.0);
 
                 u8 atkType1 = gBattleMons[opposingBattler].type1;
                 u8 atkType2 = gBattleMons[opposingBattler].type2;
                 u8 defType1 = gSpeciesInfo[species].types[0];
                 u8 defType2 = gSpeciesInfo[species].types[1];
 
-                typeEffectiveness *= GetTypeModifier(atkType1, defType1);
+                MulModifier(&typeEffectiveness, (GetTypeModifier(atkType1, defType1)));
                 if (atkType2 != atkType1)
-                    typeEffectiveness *= GetTypeModifier(atkType2, defType1);
+                    MulModifier(&typeEffectiveness, (GetTypeModifier(atkType2, defType1)));
                 if (defType2 != defType1)
                 {
-                    typeEffectiveness *= GetTypeModifier(atkType1, defType2);
+                    MulModifier(&typeEffectiveness, (GetTypeModifier(atkType1, defType2)));
                     if (atkType2 != atkType1)
-                        typeEffectiveness *= GetTypeModifier(atkType2, defType2);
+                        MulModifier(&typeEffectiveness, (GetTypeModifier(atkType2, defType2)));
                 }
                 if (typeEffectiveness < bestResist)
                 {
diff --git a/src/battle_util.c b/src/battle_util.c
index 93d02336302d..e608b0e51f78 100644
--- a/src/battle_util.c
+++ b/src/battle_util.c
@@ -8341,7 +8341,7 @@ u32 GetMoveTargetCount(u16 move, u8 battlerAtk, u8 battlerDef)
     }
 }
 
-static void MulModifier(u16 *modifier, u16 val)
+void MulModifier(u16 *modifier, u16 val)
 {
     *modifier = UQ_4_12_TO_INT((*modifier * val) + UQ_4_12_ROUND);
 }