diff --git a/packages/svelte/src/internal/client/reactivity/sources.js b/packages/svelte/src/internal/client/reactivity/sources.js
index 7db9dc49d3..7495b7ef6e 100644
--- a/packages/svelte/src/internal/client/reactivity/sources.js
+++ b/packages/svelte/src/internal/client/reactivity/sources.js
@@ -225,6 +225,8 @@ export function simple_set(source, value, should_proxy = false, needs_previous =
 
 	source.v = new_value;
 
+	source.o?.onchange?.();
+
 	return new_value;
 }
 
diff --git a/packages/svelte/tests/runtime-runes/samples/state-onchange/main.svelte b/packages/svelte/tests/runtime-runes/samples/state-onchange/main.svelte
index 11d102682a..565e8477dc 100644
--- a/packages/svelte/tests/runtime-runes/samples/state-onchange/main.svelte
+++ b/packages/svelte/tests/runtime-runes/samples/state-onchange/main.svelte
@@ -37,7 +37,7 @@
 
 
 		constructor(){
-			this.#in_constructor++;
+			this.#in_constructor = 42;
 			this.#in_constructor_proxy.count++;
 		}
 	}