diff --git a/.changeset/curvy-carrots-prove.md b/.changeset/curvy-carrots-prove.md
new file mode 100644
index 0000000000..7723990179
--- /dev/null
+++ b/.changeset/curvy-carrots-prove.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: account for mounting when `select_option` in `attribute_effect`
diff --git a/packages/svelte/src/internal/client/dom/elements/attributes.js b/packages/svelte/src/internal/client/dom/elements/attributes.js
index d0316f11b2..22e532f5e4 100644
--- a/packages/svelte/src/internal/client/dom/elements/attributes.js
+++ b/packages/svelte/src/internal/client/dom/elements/attributes.js
@@ -491,7 +491,7 @@ export function attribute_effect(
 			var current = set_attributes(element, prev, next, css_hash, skip_warning);
 
 			if (inited && is_select && 'value' in next) {
-				select_option(/** @type {HTMLSelectElement} */ (element), next.value, false);
+				select_option(/** @type {HTMLSelectElement} */ (element), next.value);
 			}
 
 			for (let symbol of Object.getOwnPropertySymbols(effects)) {
@@ -516,7 +516,7 @@ export function attribute_effect(
 			var select = /** @type {HTMLSelectElement} */ (element);
 
 			effect(() => {
-				select_option(select, /** @type {Record<string | symbol, any>} */ (prev).value);
+				select_option(select, /** @type {Record<string | symbol, any>} */ (prev).value, true);
 				init_select(select);
 			});
 		}
diff --git a/packages/svelte/src/internal/client/dom/elements/bindings/select.js b/packages/svelte/src/internal/client/dom/elements/bindings/select.js
index 5e89686d86..e39fb865cd 100644
--- a/packages/svelte/src/internal/client/dom/elements/bindings/select.js
+++ b/packages/svelte/src/internal/client/dom/elements/bindings/select.js
@@ -9,9 +9,9 @@ import * as w from '../../../warnings.js';
  * @template V
  * @param {HTMLSelectElement} select
  * @param {V} value
- * @param {boolean} [mounting]
+ * @param {boolean} mounting
  */
-export function select_option(select, value, mounting) {
+export function select_option(select, value, mounting = false) {
 	if (select.multiple) {
 		// If value is null or undefined, keep the selection as is
 		if (value == undefined) {
diff --git a/packages/svelte/tests/runtime-runes/samples/select-spread-option-selected/_config.js b/packages/svelte/tests/runtime-runes/samples/select-spread-option-selected/_config.js
new file mode 100644
index 0000000000..50da3ac095
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/select-spread-option-selected/_config.js
@@ -0,0 +1,9 @@
+import { ok, test } from '../../test';
+
+export default test({
+	async test({ assert, target, instance }) {
+		const select = target.querySelector('select');
+		ok(select);
+		assert.equal(select.selectedIndex, 1);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/select-spread-option-selected/main.svelte b/packages/svelte/tests/runtime-runes/samples/select-spread-option-selected/main.svelte
new file mode 100644
index 0000000000..e5fc6c5535
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/select-spread-option-selected/main.svelte
@@ -0,0 +1,8 @@
+<script>
+	let others = {onclick: ()=> {}}
+</script>
+
+<select {...others}>
+	<option>o1</option>
+	<option selected>o2</option>
+</select>