diff --git a/data/abilities.ts b/data/abilities.ts
index 2482241efa85..46747db16e53 100644
--- a/data/abilities.ts
+++ b/data/abilities.ts
@@ -1167,14 +1167,12 @@ export const Abilities: import('../sim/dex-abilities').AbilityDataTable = {
 	},
 	embodyaspectcornerstone: {
 		onStart(pokemon) {
-			if (pokemon.baseSpecies.name === 'Ogerpon-Cornerstone-Tera' && !this.effectState.embodied) {
-				this.effectState.embodied = true;
+			if (pokemon.baseSpecies.name === 'Ogerpon-Cornerstone-Tera' &&
+				this.effectState.embodied !== pokemon.previouslySwitchedIn) {
+				this.effectState.embodied = pokemon.previouslySwitchedIn;
 				this.boost({def: 1}, pokemon);
 			}
 		},
-		onSwitchIn() {
-			delete this.effectState.embodied;
-		},
 		flags: {failroleplay: 1, noreceiver: 1, noentrain: 1, notrace: 1, failskillswap: 1, notransform: 1},
 		name: "Embody Aspect (Cornerstone)",
 		rating: 3.5,
@@ -1182,14 +1180,12 @@ export const Abilities: import('../sim/dex-abilities').AbilityDataTable = {
 	},
 	embodyaspecthearthflame: {
 		onStart(pokemon) {
-			if (pokemon.baseSpecies.name === 'Ogerpon-Hearthflame-Tera' && !this.effectState.embodied) {
-				this.effectState.embodied = true;
+			if (pokemon.baseSpecies.name === 'Ogerpon-Hearthflame-Tera' &&
+				this.effectState.embodied !== pokemon.previouslySwitchedIn) {
+				this.effectState.embodied = pokemon.previouslySwitchedIn;
 				this.boost({atk: 1}, pokemon);
 			}
 		},
-		onSwitchIn() {
-			delete this.effectState.embodied;
-		},
 		flags: {failroleplay: 1, noreceiver: 1, noentrain: 1, notrace: 1, failskillswap: 1, notransform: 1},
 		name: "Embody Aspect (Hearthflame)",
 		rating: 3.5,
@@ -1197,14 +1193,12 @@ export const Abilities: import('../sim/dex-abilities').AbilityDataTable = {
 	},
 	embodyaspectteal: {
 		onStart(pokemon) {
-			if (pokemon.baseSpecies.name === 'Ogerpon-Teal-Tera' && !this.effectState.embodied) {
-				this.effectState.embodied = true;
+			if (pokemon.baseSpecies.name === 'Ogerpon-Teal-Tera' &&
+				this.effectState.embodied !== pokemon.previouslySwitchedIn) {
+				this.effectState.embodied = pokemon.previouslySwitchedIn;
 				this.boost({spe: 1}, pokemon);
 			}
 		},
-		onSwitchIn() {
-			delete this.effectState.embodied;
-		},
 		flags: {failroleplay: 1, noreceiver: 1, noentrain: 1, notrace: 1, failskillswap: 1, notransform: 1},
 		name: "Embody Aspect (Teal)",
 		rating: 3.5,
@@ -1212,14 +1206,12 @@ export const Abilities: import('../sim/dex-abilities').AbilityDataTable = {
 	},
 	embodyaspectwellspring: {
 		onStart(pokemon) {
-			if (pokemon.baseSpecies.name === 'Ogerpon-Wellspring-Tera' && !this.effectState.embodied) {
-				this.effectState.embodied = true;
+			if (pokemon.baseSpecies.name === 'Ogerpon-Wellspring-Tera' &&
+				this.effectState.embodied !== pokemon.previouslySwitchedIn) {
+				this.effectState.embodied = pokemon.previouslySwitchedIn;
 				this.boost({spd: 1}, pokemon);
 			}
 		},
-		onSwitchIn() {
-			delete this.effectState.embodied;
-		},
 		flags: {failroleplay: 1, noreceiver: 1, noentrain: 1, notrace: 1, failskillswap: 1, notransform: 1},
 		name: "Embody Aspect (Wellspring)",
 		rating: 3.5,
@@ -2272,18 +2264,15 @@ export const Abilities: import('../sim/dex-abilities').AbilityDataTable = {
 	},
 	libero: {
 		onPrepareHit(source, target, move) {
-			if (this.effectState.libero) return;
+			if (this.effectState.libero === source.previouslySwitchedIn) return;
 			if (move.hasBounced || move.flags['futuremove'] || move.sourceEffect === 'snatch' || move.callsMove) return;
 			const type = move.type;
 			if (type && type !== '???' && source.getTypes().join() !== type) {
 				if (!source.setType(type)) return;
-				this.effectState.libero = true;
+				this.effectState.libero = source.previouslySwitchedIn;
 				this.add('-start', source, 'typechange', type, '[from] ability: Libero');
 			}
 		},
-		onSwitchIn() {
-			delete this.effectState.libero;
-		},
 		flags: {},
 		name: "Libero",
 		rating: 4,
@@ -3416,18 +3405,15 @@ export const Abilities: import('../sim/dex-abilities').AbilityDataTable = {
 	},
 	protean: {
 		onPrepareHit(source, target, move) {
-			if (this.effectState.protean) return;
+			if (this.effectState.protean === source.previouslySwitchedIn) return;
 			if (move.hasBounced || move.flags['futuremove'] || move.sourceEffect === 'snatch' || move.callsMove) return;
 			const type = move.type;
 			if (type && type !== '???' && source.getTypes().join() !== type) {
 				if (!source.setType(type)) return;
-				this.effectState.protean = true;
+				this.effectState.protean = source.previouslySwitchedIn;
 				this.add('-start', source, 'typechange', type, '[from] ability: Protean');
 			}
 		},
-		onSwitchIn(pokemon) {
-			delete this.effectState.protean;
-		},
 		flags: {},
 		name: "Protean",
 		rating: 4,
diff --git a/data/mods/gen8/abilities.ts b/data/mods/gen8/abilities.ts
index b43d0032258d..14767f4859bd 100644
--- a/data/mods/gen8/abilities.ts
+++ b/data/mods/gen8/abilities.ts
@@ -559,7 +559,6 @@ export const Abilities: import('../../../sim/dex-abilities').ModdedAbilityDataTa
 				this.add('-start', source, 'typechange', type, '[from] ability: Libero');
 			}
 		},
-		onSwitchIn() {},
 		rating: 4.5,
 	},
 	lightmetal: {
@@ -780,7 +779,6 @@ export const Abilities: import('../../../sim/dex-abilities').ModdedAbilityDataTa
 				this.add('-start', source, 'typechange', type, '[from] ability: Protean');
 			}
 		},
-		onSwitchIn() {},
 		rating: 4.5,
 	},
 	psychicsurge: {
diff --git a/test/sim/abilities/protean.js b/test/sim/abilities/protean.js
index 8d91bbe3cea1..0c1f41a4172d 100644
--- a/test/sim/abilities/protean.js
+++ b/test/sim/abilities/protean.js
@@ -113,6 +113,73 @@ describe('Protean', function () {
 		// More examples: https://www.smogon.com/forums/threads/sword-shield-battle-mechanics-research.3655528/post-8548957
 	});
 
+	it(`should not allow the user to change its typing twice`, function () {
+		battle = common.createBattle([[
+			{species: 'Cinderace', ability: 'protean', moves: ['tackle', 'watergun']},
+		], [
+			{species: 'Gengar', moves: ['sleeptalk']},
+		]]);
+
+		battle.makeChoices();
+		const cinder = battle.p1.active[0];
+		assert(cinder.hasType('Normal'));
+
+		battle.makeChoices('move watergun', 'auto');
+		assert.false(cinder.hasType('Water'));
+	});
+
+	it(`should not allow the user to change its typing twice if the Ability was suppressed`, function () {
+		battle = common.createBattle([[
+			{species: 'Cinderace', ability: 'protean', moves: ['tackle', 'watergun']},
+		], [
+			{species: 'Gengar', moves: ['sleeptalk']},
+			{species: 'Weezing', ability: 'neutralizinggas', moves: ['sleeptalk']},
+		]]);
+
+		battle.makeChoices('move tackle', 'auto');
+		const cinder = battle.p1.active[0];
+		assert(cinder.hasType('Normal'));
+
+		battle.makeChoices('move watergun', 'switch 2');
+		battle.makeChoices('move watergun', 'switch 2');
+
+		assert.false(cinder.hasType('Water'));
+	});
+
+	it(`should allow the user to change its typing twice if it lost and regained the Ability`, function () {
+		battle = common.createBattle([[
+			{species: 'Cinderace', ability: 'protean', moves: ['tackle', 'watergun']},
+		], [
+			{species: 'Gengar', ability: 'protean', moves: ['sleeptalk', 'skillswap']},
+		]]);
+
+		battle.makeChoices('move tackle', 'move skillswap');
+		const cinder = battle.p1.active[0];
+		assert(cinder.hasType('Normal'));
+
+		battle.makeChoices('move watergun', 'auto');
+		assert(cinder.hasType('Water'));
+	});
+
+	it(`should not be prevented from resetting its effectState by Ability suppression`, function () {
+		battle = common.createBattle([[
+			{species: 'Cinderace', ability: 'protean', moves: ['tackle']},
+			{species: 'Wynaut', moves: ['sleeptalk']},
+		], [
+			{species: 'Gengar', ability: 'protean', moves: ['sleeptalk']},
+			{species: 'Weezing', ability: 'neutralizinggas', moves: ['sleeptalk']},
+		]]);
+
+		battle.makeChoices('move tackle', 'auto');
+		battle.makeChoices('move tackle', 'switch 2'); // Weezing comes in
+		battle.makeChoices('switch 2', 'auto'); // Cinderace switches out and back in
+		battle.makeChoices('switch 2', 'auto');
+		battle.makeChoices('move tackle', 'switch 2'); // Weezing switches out
+
+		const cinder = battle.p1.active[0];
+		assert(cinder.hasType('Normal'));
+	});
+
 	describe('Gen 6-8', function () {
 		it(`should activate on both turns of a charge move`, function () {
 			battle = common.gen(8).createBattle([[