diff --git a/include/config/battle.h b/include/config/battle.h
index aee79daee..5ce2e4f9f 100644
--- a/include/config/battle.h
+++ b/include/config/battle.h
@@ -115,7 +115,7 @@
 #define B_SHADOW_TAG_ESCAPE         GEN_LATEST // In Gen4+, if both sides have a Pokémon with Shadow Tag, all battlers can escape. Before, neither side could escape this situation.
 #define B_MOODY_ACC_EVASION         GEN_LATEST // In Gen8, Moody CANNOT raise Accuracy and Evasion anymore.
 #define B_FLASH_FIRE_FROZEN         GEN_LATEST // In Gen5+, Flash Fire can trigger even when frozen, when it couldn't before.
-#define B_SYNCHRONIZE_NATURE        GEN_LATEST // In Gen8, if a 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_NATURE        GEN_LATEST // In Gen8, if a Pokémon with Synchronize is leading the party, it's 100% guaranteed that wild Pokémon will have the same Nature, as opposed to 50% previously. In Gen9, it has no out-of-battle effect.
 #define B_SYNCHRONIZE_TOXIC         GEN_LATEST // In Gen5+, if a 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_LATEST // In Gen8, Intimidate doesn't work on opponents with the Inner Focus, Scrappy, Own Tempo or Oblivious abilities. It also activates Rattled.
 #define B_OBLIVIOUS_TAUNT           GEN_LATEST // In Gen6+, Pokémon with Oblivious can't be taunted.
diff --git a/src/wild_encounter.c b/src/wild_encounter.c
index 6016e08e6..5ea88f4c4 100644
--- a/src/wild_encounter.c
+++ b/src/wild_encounter.c
@@ -415,6 +415,7 @@ static u8 PickWildMonNature(void)
             }
         }
     }
+#if B_SYNCHRONIZE_NATURE < GEN_9
     // check synchronize for a pokemon with the same ability
     if (!GetMonData(&gPlayerParty[0], MON_DATA_SANITY_IS_EGG)
         && GetMonAbility(&gPlayerParty[0]) == ABILITY_SYNCHRONIZE
@@ -425,6 +426,7 @@ static u8 PickWildMonNature(void)
     {
         return GetMonData(&gPlayerParty[0], MON_DATA_PERSONALITY) % NUM_NATURES;
     }
+#endif
 
     // random nature
     return Random() % NUM_NATURES;