diff --git a/include/battle_util.h b/include/battle_util.h
index da47b3444b..2866d9072f 100644
--- a/include/battle_util.h
+++ b/include/battle_util.h
@@ -190,7 +190,7 @@ bool32 IsBattlerMegaEvolved(u32 battler);
 bool32 IsBattlerPrimalReverted(u32 battler);
 bool32 IsBattlerUltraBursted(u32 battler);
 u16 GetBattleFormChangeTargetSpecies(u32 battler, u16 method);
-bool32 TryBattleFormChange(u32 battler, u16 method);
+bool32 TryBattleFormChange(u32 battler, u32 method);
 bool32 DoBattlersShareType(u32 battler1, u32 battler2);
 bool32 CanBattlerGetOrLoseItem(u32 battler, u16 itemId);
 u32 GetIllusionMonSpecies(u32 battler);
diff --git a/src/battle_util.c b/src/battle_util.c
index 3f6067c396..ffa81eb2a7 100644
--- a/src/battle_util.c
+++ b/src/battle_util.c
@@ -10568,12 +10568,12 @@ bool32 CanBattlerFormChange(u32 battler, u16 method)
     return DoesSpeciesHaveFormChangeMethod(gBattleMons[battler].species, method);
 }
 
-bool32 TryBattleFormChange(u32 battler, u16 method)
+bool32 TryBattleFormChange(u32 battler, u32 method)
 {
-    u8 monId = gBattlerPartyIndexes[battler];
-    u8 side = GetBattlerSide(battler);
+    u32 monId = gBattlerPartyIndexes[battler];
+    u32 side = GetBattlerSide(battler);
     struct Pokemon *party = GetBattlerParty(battler);
-    u16 targetSpecies;
+    u32 targetSpecies;
 
     if (!CanBattlerFormChange(battler, method))
         return FALSE;
@@ -10611,10 +10611,14 @@ bool32 TryBattleFormChange(u32 battler, u16 method)
 
         if (restoreSpecies)
         {
+            u32 abilityForm = gBattleMons[battler].ability;
             // Reverts the original species
             TryToSetBattleFormChangeMoves(&party[monId], method);
             SetMonData(&party[monId], MON_DATA_SPECIES, &gBattleStruct->changedSpecies[side][monId]);
             RecalcBattlerStats(battler, &party[monId]);
+            // Battler data is not updated with regular form's ability, not doing so could cause wrong ability activation.
+            if (method == FORM_CHANGE_FAINT)
+                gBattleMons[battler].ability = abilityForm;
             return TRUE;
         }
     }
diff --git a/test/battle/form_change/mega_evolution.c b/test/battle/form_change/mega_evolution.c
index b2426933f7..a42c003a3d 100644
--- a/test/battle/form_change/mega_evolution.c
+++ b/test/battle/form_change/mega_evolution.c
@@ -153,3 +153,26 @@ SINGLE_BATTLE_TEST("Regular Mega Evolution and Fervent Wish Mega Evolution can h
         EXPECT_EQ(opponent->species, SPECIES_GARDEVOIR_MEGA);
     }
 }
+
+SINGLE_BATTLE_TEST("Mega Evolved Pokemon do not change abilities after fainting")
+{
+    GIVEN {
+        ASSUME(gMovesInfo[MOVE_CRUNCH].makesContact == TRUE);
+        ASSUME(gSpeciesInfo[SPECIES_GARCHOMP_MEGA].abilities[0] != ABILITY_ROUGH_SKIN);
+        ASSUME(gSpeciesInfo[SPECIES_GARCHOMP_MEGA].abilities[1] != ABILITY_ROUGH_SKIN);
+        ASSUME(gSpeciesInfo[SPECIES_GARCHOMP_MEGA].abilities[2] != ABILITY_ROUGH_SKIN);
+        PLAYER(SPECIES_WOBBUFFET);
+        OPPONENT(SPECIES_GARCHOMP) { Ability(ABILITY_ROUGH_SKIN); Item(ITEM_GARCHOMPITE); HP(1); }
+    } WHEN {
+        TURN { MOVE(player, MOVE_CRUNCH); MOVE(opponent, MOVE_CELEBRATE, megaEvolve: TRUE); }
+    } SCENE {
+        ANIMATION(ANIM_TYPE_GENERAL, B_ANIM_MEGA_EVOLUTION, opponent);
+        ANIMATION(ANIM_TYPE_MOVE, MOVE_CRUNCH, player);
+        MESSAGE("Foe Garchomp fainted!");
+        NONE_OF {
+            ABILITY_POPUP(opponent, ABILITY_ROUGH_SKIN);
+            MESSAGE("Wobbuffet was hurt by Foe Garchomp's Rough Skin!");
+            HP_BAR(player);
+        }
+    }
+}