diff --git a/include/constants/battle_config.h b/include/constants/battle_config.h
index 95ff4f4a04..1c77819808 100644
--- a/include/constants/battle_config.h
+++ b/include/constants/battle_config.h
@@ -162,6 +162,7 @@
 #define B_MOODY_ACC_EVASION         GEN_8 // In Gen8, Moody CANNOT raise Accuracy and Evasion anymore.
 #define B_FLASH_FIRE_FROZEN         GEN_7 // In Gen5+, Flash Fire can trigger even when frozen, when it couldn't before.
 #define B_SYNCHRONIZE_NATURE        GEN_8 // In Gen8, if the Pokémon with Synchronize is leading the party, it's 100% guaranteed that wild Pokémon will have the same ability, as opposed to 50% previously.
+#define B_SYNCHRONIZE_TOXIC         GEN_8 // In Gen5+, if the Pokémon with Synchronize is badly poisoned, the opponent will also become badly poisoned. Previously, the opponent would become regular poisoned.
 #define B_UPDATED_INTIMIDATE        GEN_8 // In Gen8, Intimidate doesn't work on opponents with the Inner Focus, Scrappy, Own Tempo or Oblivious abilities.
 
 // Item settings
diff --git a/src/battle_util.c b/src/battle_util.c
index 0585bb4b62..3ddc2e9bb0 100644
--- a/src/battle_util.c
+++ b/src/battle_util.c
@@ -5471,8 +5471,10 @@ u8 AbilityBattleEffects(u8 caseID, u8 battler, u16 ability, u8 special, u16 move
             if (!(gBattleMons[gBattlerAttacker].status1 & STATUS1_ANY))
             {
                 gBattleStruct->synchronizeMoveEffect &= ~(MOVE_EFFECT_AFFECTS_USER | MOVE_EFFECT_CERTAIN);
-                if (gBattleStruct->synchronizeMoveEffect == MOVE_EFFECT_TOXIC)
-                    gBattleStruct->synchronizeMoveEffect = MOVE_EFFECT_POISON;
+                #if B_SYNCHRONIZE_TOXIC < GEN_5
+                    if (gBattleStruct->synchronizeMoveEffect == MOVE_EFFECT_TOXIC)
+                        gBattleStruct->synchronizeMoveEffect = MOVE_EFFECT_POISON;
+                #endif
 
                 gBattleScripting.moveEffect = gBattleStruct->synchronizeMoveEffect + MOVE_EFFECT_AFFECTS_USER;
                 gBattleScripting.battler = gBattlerAbility = gBattlerTarget;