diff --git a/packages/svelte/messages/compile-errors/template.md b/packages/svelte/messages/compile-errors/template.md
index bacd9c50d8..b35d83cf8f 100644
--- a/packages/svelte/messages/compile-errors/template.md
+++ b/packages/svelte/messages/compile-errors/template.md
@@ -30,10 +30,6 @@
 
 > Event attribute must be a JavaScript expression, not a string
 
-## attribute_invalid_expression
-
-> Invalid attribute expression
-
 ## attribute_invalid_multiple
 
 > 'multiple' attribute must be static if select uses two-way binding
@@ -50,6 +46,10 @@
 
 > 'type' attribute must be a static text value if input uses two-way binding
 
+## attribute_unquoted_sequence
+
+> Attribute values containing `{...}` must be enclosed in quote marks, unless the value only contains the expression
+
 ## bind_invalid_expression
 
 > Can only bind to an Identifier or MemberExpression
diff --git a/packages/svelte/src/compiler/errors.js b/packages/svelte/src/compiler/errors.js
index a18e145332..df75245a68 100644
--- a/packages/svelte/src/compiler/errors.js
+++ b/packages/svelte/src/compiler/errors.js
@@ -600,15 +600,6 @@ export function attribute_invalid_event_handler(node) {
 	e(node, "attribute_invalid_event_handler", "Event attribute must be a JavaScript expression, not a string");
 }
 
-/**
- * Invalid attribute expression
- * @param {null | number | NodeLike} node
- * @returns {never}
- */
-export function attribute_invalid_expression(node) {
-	e(node, "attribute_invalid_expression", "Invalid attribute expression");
-}
-
 /**
  * 'multiple' attribute must be static if select uses two-way binding
  * @param {null | number | NodeLike} node
@@ -646,6 +637,15 @@ export function attribute_invalid_type(node) {
 	e(node, "attribute_invalid_type", "'type' attribute must be a static text value if input uses two-way binding");
 }
 
+/**
+ * Attribute values containing `{...}` must be enclosed in quote marks, unless the value only contains the expression
+ * @param {null | number | NodeLike} node
+ * @returns {never}
+ */
+export function attribute_unquoted_sequence(node) {
+	e(node, "attribute_unquoted_sequence", "Attribute values containing `{...}` must be enclosed in quote marks, unless the value only contains the expression");
+}
+
 /**
  * Can only bind to an Identifier or MemberExpression
  * @param {null | number | NodeLike} node
diff --git a/packages/svelte/src/compiler/phases/2-analyze/validation.js b/packages/svelte/src/compiler/phases/2-analyze/validation.js
index d05fbcb4fa..7bf9773800 100644
--- a/packages/svelte/src/compiler/phases/2-analyze/validation.js
+++ b/packages/svelte/src/compiler/phases/2-analyze/validation.js
@@ -9,7 +9,6 @@ import {
 	extract_identifiers,
 	get_parent,
 	is_expression_attribute,
-	is_quoted_attribute,
 	is_text_attribute,
 	object,
 	unwrap_optional
@@ -34,6 +33,17 @@ import { Scope, get_rune } from '../scope.js';
 import { merge } from '../visitors.js';
 import { a11y_validators } from './a11y.js';
 
+/** @param {import('#compiler').Attribute} attribute */
+function validate_attribute(attribute) {
+	if (attribute.value === true || attribute.value.length === 1) return;
+
+	const is_quoted = attribute.value.at(-1)?.end !== attribute.end;
+
+	if (!is_quoted) {
+		e.attribute_unquoted_sequence(attribute);
+	}
+}
+
 /**
  * @param {import('#compiler').Component | import('#compiler').SvelteComponent | import('#compiler').SvelteSelf} node
  * @param {import('zimmerframe').Context<import('#compiler').SvelteNode, import('./types.js').AnalysisState>} context
@@ -58,23 +68,18 @@ function validate_component(node, context) {
 		}
 
 		if (attribute.type === 'Attribute') {
-			if (
-				context.state.analysis.runes &&
-				!is_quoted_attribute(attribute) &&
-				Array.isArray(attribute.value) &&
-				attribute.value.length > 1
-			) {
-				e.attribute_invalid_expression(attribute);
-			}
-
-			if (context.state.analysis.runes && is_expression_attribute(attribute)) {
-				const expression = attribute.value[0].expression;
-				if (expression.type === 'SequenceExpression') {
-					let i = /** @type {number} */ (expression.start);
-					while (--i > 0) {
-						const char = context.state.analysis.source[i];
-						if (char === '(') break; // parenthesized sequence expressions are ok
-						if (char === '{') e.attribute_invalid_sequence_expression(expression);
+			if (context.state.analysis.runes) {
+				validate_attribute(attribute);
+
+				if (is_expression_attribute(attribute)) {
+					const expression = attribute.value[0].expression;
+					if (expression.type === 'SequenceExpression') {
+						let i = /** @type {number} */ (expression.start);
+						while (--i > 0) {
+							const char = context.state.analysis.source[i];
+							if (char === '(') break; // parenthesized sequence expressions are ok
+							if (char === '{') e.attribute_invalid_sequence_expression(expression);
+						}
 					}
 				}
 			}
@@ -116,23 +121,18 @@ function validate_element(node, context) {
 		if (attribute.type === 'Attribute') {
 			const is_expression = is_expression_attribute(attribute);
 
-			if (
-				context.state.analysis.runes &&
-				!is_quoted_attribute(attribute) &&
-				Array.isArray(attribute.value) &&
-				attribute.value.length > 1
-			) {
-				e.attribute_invalid_expression(attribute);
-			}
-
-			if (context.state.analysis.runes && is_expression) {
-				const expression = attribute.value[0].expression;
-				if (expression.type === 'SequenceExpression') {
-					let i = /** @type {number} */ (expression.start);
-					while (--i > 0) {
-						const char = context.state.analysis.source[i];
-						if (char === '(') break; // parenthesized sequence expressions are ok
-						if (char === '{') e.attribute_invalid_sequence_expression(expression);
+			if (context.state.analysis.runes) {
+				validate_attribute(attribute);
+
+				if (is_expression) {
+					const expression = attribute.value[0].expression;
+					if (expression.type === 'SequenceExpression') {
+						let i = /** @type {number} */ (expression.start);
+						while (--i > 0) {
+							const char = context.state.analysis.source[i];
+							if (char === '(') break; // parenthesized sequence expressions are ok
+							if (char === '{') e.attribute_invalid_sequence_expression(expression);
+						}
 					}
 				}
 			}
diff --git a/packages/svelte/src/compiler/utils/ast.js b/packages/svelte/src/compiler/utils/ast.js
index 747956ab86..7a5062382f 100644
--- a/packages/svelte/src/compiler/utils/ast.js
+++ b/packages/svelte/src/compiler/utils/ast.js
@@ -44,16 +44,6 @@ export function is_expression_attribute(attribute) {
 	);
 }
 
-/**
- * Returns true if the attribute is quoted.
- * @param {import('#compiler').Attribute} attribute
- * @returns {attribute is import('#compiler').Attribute & { value: [import('#compiler').ExpressionTag] }}
- */
-export function is_quoted_attribute(attribute) {
-	if (attribute.value === true) return false;
-	return attribute.value.at(-1)?.end !== attribute.end;
-}
-
 /**
  * Returns true if the attribute starts with `on` and contains a single expression node.
  * @param {import('#compiler').Attribute} attribute
diff --git a/packages/svelte/tests/compiler-errors/samples/unbalanced-curly-component/_config.js b/packages/svelte/tests/compiler-errors/samples/unbalanced-curly-component/_config.js
index 77d662ebc7..cd3a73a1c7 100644
--- a/packages/svelte/tests/compiler-errors/samples/unbalanced-curly-component/_config.js
+++ b/packages/svelte/tests/compiler-errors/samples/unbalanced-curly-component/_config.js
@@ -2,8 +2,9 @@ import { test } from '../../test';
 
 export default test({
 	error: {
-		code: 'attribute_invalid_expression',
-		message: 'Invalid attribute expression',
+		code: 'attribute_unquoted_sequence',
+		message:
+			'Attribute values containing `{...}` must be enclosed in quote marks, unless the value only contains the expression',
 		position: [101, 116]
 	}
 });
diff --git a/packages/svelte/tests/compiler-errors/samples/unbalanced-curly-element/_config.js b/packages/svelte/tests/compiler-errors/samples/unbalanced-curly-element/_config.js
index db927e8399..4ce7a3d285 100644
--- a/packages/svelte/tests/compiler-errors/samples/unbalanced-curly-element/_config.js
+++ b/packages/svelte/tests/compiler-errors/samples/unbalanced-curly-element/_config.js
@@ -2,8 +2,9 @@ import { test } from '../../test';
 
 export default test({
 	error: {
-		code: 'attribute_invalid_expression',
-		message: 'Invalid attribute expression',
+		code: 'attribute_unquoted_sequence',
+		message:
+			'Attribute values containing `{...}` must be enclosed in quote marks, unless the value only contains the expression',
 		position: [34, 71]
 	}
 });
diff --git a/packages/svelte/tests/compiler-errors/samples/unbalanced-curly-element/main.svelte b/packages/svelte/tests/compiler-errors/samples/unbalanced-curly-element/main.svelte
index 0d9bbce366..0ea66fecb0 100644
--- a/packages/svelte/tests/compiler-errors/samples/unbalanced-curly-element/main.svelte
+++ b/packages/svelte/tests/compiler-errors/samples/unbalanced-curly-element/main.svelte
@@ -3,4 +3,4 @@
 	onclick={() => console.log('hello')}}
 >
 	click
-</button>
\ No newline at end of file
+</button>