diff --git a/documentation/docs/98-reference/.generated/compile-errors.md b/documentation/docs/98-reference/.generated/compile-errors.md
index 079b1d2a0a..1c874436de 100644
--- a/documentation/docs/98-reference/.generated/compile-errors.md
+++ b/documentation/docs/98-reference/.generated/compile-errors.md
@@ -63,9 +63,29 @@ Event attribute must be a JavaScript expression, not a string
 ### attribute_invalid_sequence_expression
 
 ```
-Sequence expressions are not allowed as attribute/directive values in runes mode, unless wrapped in parentheses
+Comma-separated expressions are not allowed as attribute/directive values in runes mode, unless wrapped in parentheses
 ```
 
+An attribute value cannot be a comma-separated sequence of expressions — in other words this is disallowed:
+
+```svelte
+<div class={size, color}>...</div>
+```
+
+Instead, make sure that the attribute value contains a single expression. In the example above it's likely that this was intended (see the [class documentation](class) for more details):
+
+```svelte
+<div class={[size, color]}>...</div>
+```
+
+If you _do_ need to use the comma operator for some reason, wrap the sequence in parentheses:
+
+```svelte
+<div class={(size, color)}>...</div>
+```
+
+Note that this will evaluate to `color`, ignoring `size`.
+
 ### attribute_invalid_type
 
 ```
diff --git a/packages/svelte/messages/compile-errors/template.md b/packages/svelte/messages/compile-errors/template.md
index bd07955bc3..6aa4335c11 100644
--- a/packages/svelte/messages/compile-errors/template.md
+++ b/packages/svelte/messages/compile-errors/template.md
@@ -40,7 +40,27 @@
 
 ## attribute_invalid_sequence_expression
 
-> Sequence expressions are not allowed as attribute/directive values in runes mode, unless wrapped in parentheses
+> Comma-separated expressions are not allowed as attribute/directive values in runes mode, unless wrapped in parentheses
+
+An attribute value cannot be a comma-separated sequence of expressions — in other words this is disallowed:
+
+```svelte
+<div class={size, color}>...</div>
+```
+
+Instead, make sure that the attribute value contains a single expression. In the example above it's likely that this was intended (see the [class documentation](class) for more details):
+
+```svelte
+<div class={[size, color]}>...</div>
+```
+
+If you _do_ need to use the comma operator for some reason, wrap the sequence in parentheses:
+
+```svelte
+<div class={(size, color)}>...</div>
+```
+
+Note that this will evaluate to `color`, ignoring `size`.
 
 ## attribute_invalid_type
 
diff --git a/packages/svelte/src/compiler/errors.js b/packages/svelte/src/compiler/errors.js
index 3997dbec32..c28c737d7f 100644
--- a/packages/svelte/src/compiler/errors.js
+++ b/packages/svelte/src/compiler/errors.js
@@ -785,12 +785,12 @@ export function attribute_invalid_name(node, name) {
 }
 
 /**
- * Sequence expressions are not allowed as attribute/directive values in runes mode, unless wrapped in parentheses
+ * Comma-separated expressions are not allowed as attribute/directive values in runes mode, unless wrapped in parentheses
  * @param {null | number | NodeLike} node
  * @returns {never}
  */
 export function attribute_invalid_sequence_expression(node) {
-	e(node, 'attribute_invalid_sequence_expression', `Sequence expressions are not allowed as attribute/directive values in runes mode, unless wrapped in parentheses\nhttps://svelte.dev/e/attribute_invalid_sequence_expression`);
+	e(node, 'attribute_invalid_sequence_expression', `Comma-separated expressions are not allowed as attribute/directive values in runes mode, unless wrapped in parentheses\nhttps://svelte.dev/e/attribute_invalid_sequence_expression`);
 }
 
 /**
diff --git a/packages/svelte/tests/compiler-errors/samples/attribute-sequence-expression-2/_config.js b/packages/svelte/tests/compiler-errors/samples/attribute-sequence-expression-2/_config.js
index 13d7f9c66b..55f02e801b 100644
--- a/packages/svelte/tests/compiler-errors/samples/attribute-sequence-expression-2/_config.js
+++ b/packages/svelte/tests/compiler-errors/samples/attribute-sequence-expression-2/_config.js
@@ -4,7 +4,7 @@ export default test({
 	error: {
 		code: 'attribute_invalid_sequence_expression',
 		message:
-			'Sequence expressions are not allowed as attribute/directive values in runes mode, unless wrapped in parentheses',
+			'Comma-separated expressions are not allowed as attribute/directive values in runes mode, unless wrapped in parentheses',
 		position: [124, 131]
 	}
 });
diff --git a/packages/svelte/tests/compiler-errors/samples/attribute-sequence-expression/_config.js b/packages/svelte/tests/compiler-errors/samples/attribute-sequence-expression/_config.js
index 4fb1680d01..1c50ef76ea 100644
--- a/packages/svelte/tests/compiler-errors/samples/attribute-sequence-expression/_config.js
+++ b/packages/svelte/tests/compiler-errors/samples/attribute-sequence-expression/_config.js
@@ -4,7 +4,7 @@ export default test({
 	error: {
 		code: 'attribute_invalid_sequence_expression',
 		message:
-			'Sequence expressions are not allowed as attribute/directive values in runes mode, unless wrapped in parentheses',
+			'Comma-separated expressions are not allowed as attribute/directive values in runes mode, unless wrapped in parentheses',
 		position: [163, 170]
 	}
 });