diff --git a/packages/svelte/src/compiler/phases/3-transform/client/visitors/RegularElement.js b/packages/svelte/src/compiler/phases/3-transform/client/visitors/RegularElement.js
index 1c4a75fb16..d1348a9e5e 100644
--- a/packages/svelte/src/compiler/phases/3-transform/client/visitors/RegularElement.js
+++ b/packages/svelte/src/compiler/phases/3-transform/client/visitors/RegularElement.js
@@ -496,7 +496,7 @@ export function build_class_directives_object(
  * @param {ComponentContext} context
  * @param {MemoizedExpression[]} async_expressions
  * @param {MemoizedExpression[]} expressions
- * @return {ObjectExpression | ArrayExpression}}
+ * @return {ObjectExpression | ArrayExpression | Identifier}}
  */
 export function build_style_directives_object(
 	style_directives,
@@ -506,28 +506,33 @@ export function build_style_directives_object(
 ) {
 	let normal_properties = [];
 	let important_properties = [];
+	let has_call_or_state = false;
+	let has_await = false;
 
-	for (const directive of style_directives) {
+	for (const d of style_directives) {
 		const expression =
-			directive.value === true
-				? build_getter({ name: directive.name, type: 'Identifier' }, context.state)
-				: build_attribute_value(directive.value, context, (value, metadata) =>
-						metadata.has_call
-							? get_expression_id(metadata.has_await ? async_expressions : expressions, value)
-							: value
-					).value;
-		const property = b.init(directive.name, expression);
+			d.value === true
+				? build_getter({ name: d.name, type: 'Identifier' }, context.state)
+				: build_attribute_value(d.value, context).value;
+		const property = b.init(d.name, expression);
 
-		if (directive.modifiers.includes('important')) {
+		if (d.modifiers.includes('important')) {
 			important_properties.push(property);
 		} else {
 			normal_properties.push(property);
 		}
+
+		has_call_or_state ||= d.metadata.expression.has_call || d.metadata.expression.has_state;
+		has_await ||= d.metadata.expression.has_await;
 	}
 
-	return important_properties.length
+	const directives = important_properties.length
 		? b.array([b.object(normal_properties), b.object(important_properties)])
 		: b.object(normal_properties);
+
+	return has_call_or_state || has_await
+		? get_expression_id(has_await ? async_expressions : expressions, directives)
+		: directives;
 }
 
 /**
diff --git a/packages/svelte/src/compiler/phases/3-transform/client/visitors/shared/element.js b/packages/svelte/src/compiler/phases/3-transform/client/visitors/shared/element.js
index b1b1a8fae4..868cfe2946 100644
--- a/packages/svelte/src/compiler/phases/3-transform/client/visitors/shared/element.js
+++ b/packages/svelte/src/compiler/phases/3-transform/client/visitors/shared/element.js
@@ -87,18 +87,24 @@ export function build_attribute_effect(
 		);
 	}
 
+	const all = [...expressions, ...async_expressions];
+
+	for (let i = 0; i < all.length; i += 1) {
+		all[i].id.name = `$${i}`;
+	}
+
 	context.state.init.push(
 		b.stmt(
 			b.call(
 				'$.attribute_effect',
 				element_id,
 				b.arrow(
-					expressions.map(({ id }) => id),
+					all.map(({ id }) => id),
 					b.object(values)
 				),
 				expressions.length > 0 && b.array(expressions.map(({ expression }) => b.thunk(expression))),
 				async_expressions.length > 0 &&
-					b.array(async_expressions.map(({ expression }) => b.thunk(expression))),
+					b.array(async_expressions.map(({ expression }) => b.thunk(expression, true))),
 				element.metadata.scoped &&
 					context.state.analysis.css.hash !== '' &&
 					b.literal(context.state.analysis.css.hash),
@@ -182,7 +188,9 @@ export function build_set_class(element, node_id, attribute, class_directives, c
 
 	if (class_directives.length) {
 		next = build_class_directives_object(class_directives, context);
-		has_state ||= class_directives.some((d) => d.metadata.expression.has_state);
+		has_state ||= class_directives.some(
+			(d) => d.metadata.expression.has_state || d.metadata.expression.has_await
+		);
 
 		if (has_state) {
 			previous_id = b.id(context.state.scope.generate('classes'));
@@ -255,7 +263,9 @@ export function build_set_style(node_id, attribute, style_directives, context) {
 
 	if (style_directives.length) {
 		next = build_style_directives_object(style_directives, context);
-		has_state ||= style_directives.some((d) => d.metadata.expression.has_state);
+		has_state ||= style_directives.some(
+			(d) => d.metadata.expression.has_state || d.metadata.expression.has_await
+		);
 
 		if (has_state) {
 			previous_id = b.id(context.state.scope.generate('styles'));
diff --git a/packages/svelte/tests/runtime-runes/samples/async-class-directive/_config.js b/packages/svelte/tests/runtime-runes/samples/async-class-directive/_config.js
new file mode 100644
index 0000000000..3186ed2069
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-class-directive/_config.js
@@ -0,0 +1,20 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	html: `loading`,
+
+	async test({ assert, target }) {
+		await tick();
+
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+				<div class="one">one</div>
+				<div class="two">two</div>
+				<div style="color: red;">red</div>
+				<div style="color: blue;">blue</div>
+			`
+		);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-class-directive/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-class-directive/main.svelte
new file mode 100644
index 0000000000..f0f27e4830
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-class-directive/main.svelte
@@ -0,0 +1,11 @@
+<svelte:boundary>
+	<div class:one={await true} {...{}}>one</div>
+	<div class:two={await true}>two</div>
+
+	<div style:color={await 'red'} {...{}}>red</div>
+	<div style:color={await 'blue'}>blue</div>
+
+	{#snippet pending()}
+		loading
+	{/snippet}
+</svelte:boundary>