diff --git a/src/data/ability.ts b/src/data/ability.ts
index 972da7741ad..7de7d809460 100644
--- a/src/data/ability.ts
+++ b/src/data/ability.ts
@@ -2591,7 +2591,8 @@ export function initAbilities() {
     new Ability(Abilities.EMBODY_ASPECT_WELLSPRING, "Embody Aspect (N)", "The Pokémon's heart fills with memories, causing the Wellspring Mask to shine and the Pokémon's Sp. Def stat to be boosted.", 9),
     new Ability(Abilities.EMBODY_ASPECT_HEARTHFLAME, "Embody Aspect (N)", "The Pokémon's heart fills with memories, causing the Hearthflame Mask to shine and the Pokémon's Attack stat to be boosted.", 9),
     new Ability(Abilities.EMBODY_ASPECT_CORNERSTONE, "Embody Aspect (N)", "The Pokémon's heart fills with memories, causing the Cornerstone Mask to shine and the Pokémon's Defense stat to be boosted.", 9),
-    new Ability(Abilities.TERA_SHIFT, "Tera Shift (N)", "When the Pokémon enters a battle, it absorbs the energy around itself and transforms into its Terastal Form.", 9),
+    new Ability(Abilities.TERA_SHIFT, "Tera Shift", "When the Pokémon enters a battle, it absorbs the energy around itself and transforms into its Terastal Form.", 9)
+      .attr(PostSummonFormChangeAbAttr, p => p.getFormKey() ? 0 : 1),
     new Ability(Abilities.TERA_SHELL, "Tera Shell (N)", "The Pokémon's shell contains the powers of each type. All damage-dealing moves that hit the Pokémon when its HP is full will not be very effective.", 9)
       .ignorable(),
     new Ability(Abilities.TERAFORM_ZERO, "Teraform Zero (N)", "When Terapagos changes into its Stellar Form, it uses its hidden powers to eliminate all effects of weather and terrain, reducing them to zero.", 9),
diff --git a/src/data/pokemon-forms.ts b/src/data/pokemon-forms.ts
index 79d8b0be1ff..805933d283b 100644
--- a/src/data/pokemon-forms.ts
+++ b/src/data/pokemon-forms.ts
@@ -608,6 +608,9 @@ export const pokemonFormChanges: PokemonFormChanges = {
     new SpeciesFormChange(Species.OGERPON, 'teal-mask', 'wellspring-mask', new SpeciesFormChangeItemTrigger(FormChangeItem.WELLSPRING_MASK)),
     new SpeciesFormChange(Species.OGERPON, 'teal-mask', 'hearthflame-mask', new SpeciesFormChangeItemTrigger(FormChangeItem.HEARTHFLAME_MASK)),
     new SpeciesFormChange(Species.OGERPON, 'teal-mask', 'cornerstone-mask', new SpeciesFormChangeItemTrigger(FormChangeItem.CORNERSTONE_MASK))
+  ],
+  [Species.TERAPAGOS]: [
+    new SpeciesFormChange(Species.TERAPAGOS, '', 'terastal', new SpeciesFormChangeManualTrigger(), true)
   ]
 };