diff --git a/packages/svelte/CHANGELOG.md b/packages/svelte/CHANGELOG.md
index e254be754f..ef64091ca3 100644
--- a/packages/svelte/CHANGELOG.md
+++ b/packages/svelte/CHANGELOG.md
@@ -1,5 +1,11 @@
 # svelte
 
+## 5.34.9
+
+### Patch Changes
+
+- fix: ensure unowned deriveds can add themselves as reactions while connected ([#16249](https://github.com/sveltejs/svelte/pull/16249))
+
 ## 5.34.8
 
 ### Patch Changes
diff --git a/packages/svelte/package.json b/packages/svelte/package.json
index 17a3e980c4..1d26663143 100644
--- a/packages/svelte/package.json
+++ b/packages/svelte/package.json
@@ -2,7 +2,7 @@
   "name": "svelte",
   "description": "Cybernetically enhanced web apps",
   "license": "MIT",
-  "version": "5.34.8",
+  "version": "5.34.9",
   "type": "module",
   "types": "./types/index.d.ts",
   "engines": {
diff --git a/packages/svelte/src/internal/client/runtime.js b/packages/svelte/src/internal/client/runtime.js
index 56bc157f33..d057bfdf0d 100644
--- a/packages/svelte/src/internal/client/runtime.js
+++ b/packages/svelte/src/internal/client/runtime.js
@@ -294,7 +294,12 @@ export function update_reaction(reaction) {
 				reaction.deps = deps = new_deps;
 			}
 
-			if (!skip_reaction) {
+			if (
+				!skip_reaction ||
+				// Deriveds that already have reactions can cleanup, so we still add them as reactions
+				((flags & DERIVED) !== 0 &&
+					/** @type {import('#client').Derived} */ (reaction).reactions !== null)
+			) {
 				for (i = skipped_deps; i < deps.length; i++) {
 					(deps[i].reactions ??= []).push(reaction);
 				}
diff --git a/packages/svelte/src/version.js b/packages/svelte/src/version.js
index ec0126b17d..1c0aed6e87 100644
--- a/packages/svelte/src/version.js
+++ b/packages/svelte/src/version.js
@@ -4,5 +4,5 @@
  * The current version, as set in package.json.
  * @type {string}
  */
-export const VERSION = '5.34.8';
+export const VERSION = '5.34.9';
 export const PUBLIC_VERSION = '5';
diff --git a/packages/svelte/tests/signals/test.ts b/packages/svelte/tests/signals/test.ts
index 78d7919e0f..719c936df0 100644
--- a/packages/svelte/tests/signals/test.ts
+++ b/packages/svelte/tests/signals/test.ts
@@ -112,6 +112,45 @@ describe('signals', () => {
 		};
 	});
 
+	test('unowned deriveds are not added as reactions but trigger effects', () => {
+		var obj = state<any>(undefined);
+
+		class C1 {
+			#v = state(0);
+			get v() {
+				return $.get(this.#v);
+			}
+			set v(v: number) {
+				set(this.#v, v);
+			}
+		}
+
+		return () => {
+			let d = derived(() => $.get(obj)?.v || '-');
+
+			const log: number[] = [];
+			assert.equal($.get(d), '-');
+
+			let destroy = effect_root(() => {
+				render_effect(() => {
+					log.push($.get(d));
+				});
+			});
+
+			set(obj, new C1());
+			flushSync();
+			assert.equal($.get(d), '-');
+			$.get(obj).v = 1;
+			flushSync();
+			assert.equal($.get(d), 1);
+			assert.deepEqual(log, ['-', 1]);
+			destroy();
+			// ensure we're not leaking reactions
+			assert.equal(obj.reactions, null);
+			assert.equal(d.reactions, null);
+		};
+	});
+
 	test('derived from state', () => {
 		const log: number[] = [];