diff --git a/data/abilities.ts b/data/abilities.ts
index 4e1f52178f..cd27dfd684 100644
--- a/data/abilities.ts
+++ b/data/abilities.ts
@@ -100,6 +100,7 @@ export const Abilities: {[abilityid: string]: AbilityData} = {
 			this.eachEvent('WeatherChange', this.effect);
 		},
 		onEnd(pokemon) {
+			pokemon.abilityState.ending = true;
 			this.eachEvent('WeatherChange', this.effect);
 		},
 		suppressWeather: true,
@@ -544,6 +545,7 @@ export const Abilities: {[abilityid: string]: AbilityData} = {
 			this.eachEvent('WeatherChange', this.effect);
 		},
 		onEnd(pokemon) {
+			pokemon.abilityState.ending = true;
 			this.eachEvent('WeatherChange', this.effect);
 		},
 		suppressWeather: true,
@@ -3420,11 +3422,11 @@ export const Abilities: {[abilityid: string]: AbilityData} = {
 			this.singleEvent('WeatherChange', this.effect, this.effectState, pokemon);
 		},
 		onWeatherChange(pokemon) {
-			// Protosynthesis is not affected by Utility Umbrella, or any weather supressing ability
-			// As a result, we check the weather directly instead of via field#isWeather which calls field#effectiveWeather
-			if (this.field.weather === 'sunnyday') {
+			// Protosynthesis is not affected by Utility Umbrella
+			if (this.field.isWeather('sunnyday')) {
 				pokemon.addVolatile('protosynthesis');
-			} else if (!pokemon.volatiles['protosynthesis']?.fromBooster) {
+			} else if (!pokemon.volatiles['protosynthesis']?.fromBooster && this.field.weather !== 'sunnyday') {
+				// Protosynthesis will not deactivite if Sun is suppressed, hence the direct ID check (isWeather respects supression)
 				pokemon.removeVolatile('protosynthesis');
 			}
 		},
diff --git a/sim/field.ts b/sim/field.ts
index 2e0e975b37..067c92d1b0 100644
--- a/sim/field.ts
+++ b/sim/field.ts
@@ -106,7 +106,8 @@ export class Field {
 	suppressingWeather() {
 		for (const side of this.battle.sides) {
 			for (const pokemon of side.active) {
-				if (pokemon && !pokemon.fainted && !pokemon.ignoringAbility() && pokemon.getAbility().suppressWeather) {
+				if (pokemon && !pokemon.fainted && !pokemon.ignoringAbility() &&
+					pokemon.getAbility().suppressWeather && !pokemon.abilityState.ending) {
 					return true;
 				}
 			}
diff --git a/test/sim/abilities/protosynthesis.js b/test/sim/abilities/protosynthesis.js
index 32f0e9548f..4159c47ef8 100644
--- a/test/sim/abilities/protosynthesis.js
+++ b/test/sim/abilities/protosynthesis.js
@@ -77,16 +77,46 @@ describe('Protosynthesis', function () {
 		assert.equal(tail.volatiles['protosynthesis'].bestStat, 'spd', `Scream Tail's SpD should have been boosted by Protosynthesis in Sun while holding Utility Umbrella`);
 	});
 
-	it(`should not be prevented from activating by weather suppressing abilities`, function () {
+	it(`should not be deactiviated by weather suppressing abilities`, function () {
 		battle = common.createBattle([[
 			{species: 'Scream Tail', ability: 'protosynthesis', moves: ['splash']},
 		], [
-			{species: 'Altaria', ability: 'cloudnine', moves: ['sunnyday']},
+			{species: 'Torkoal', ability: 'drought', moves: ['splash']},
+			{species: 'Psyduck', ability: 'cloudnine', moves: ['splash']},
+		]]);
+
+		const tail = battle.p1.active[0];
+		battle.makeChoices('move splash', 'switch 2');
+
+		assert.equal(tail.volatiles['protosynthesis'].bestStat, 'spd', `Scream Tail's SpD should have remained boosted by Protosynthesis in Sun even though a weather supressing ability was activated`);
+	});
+
+	it(`should not activate if weather is suppressed`, function () {
+		battle = common.createBattle([[
+			{species: 'Scream Tail', ability: 'protosynthesis', moves: ['splash']},
+		], [
+			{species: 'Psyduck', ability: 'cloudnine', moves: ['sunnyday']},
 		]]);
 
 		const tail = battle.p1.active[0];
 		battle.makeChoices('move splash', 'move sunnyday');
-		assert.equal(tail.volatiles['protosynthesis'].bestStat, 'spd', `Scream Tail's SpD should have been boosted by Protosynthesis in Sun even though a weather supressing ability was active`);
+
+		assert.equal(tail.volatiles['protosynthesis'], undefined, `Scream Tail should not have been boosted by Protosynthesis because a weather supressing ability was active when Sun started`);
+	});
+
+	it(`should activate when weather supression ends`, function () {
+		battle = common.createBattle([[
+			{species: 'Scream Tail', ability: 'protosynthesis', moves: ['splash']},
+		], [
+			{species: 'Psyduck', ability: 'cloudnine', moves: ['sunnyday']},
+			{species: 'Lotad', ability: 'swiftswim', moves: ['splash']},
+		]]);
+
+		const tail = battle.p1.active[0];
+		battle.makeChoices('move splash', 'move sunnyday');
+		battle.makeChoices('move splash', 'switch 2');
+
+		assert.equal(tail.volatiles['protosynthesis'].bestStat, 'spd', `Scream Tail should have been boosted by Protosynthesis because a weather supressing ability ended while Sun was active`);
 	});
 
 	it(`should have its boost nullified by Neutralizing Gas`, function () {