diff --git a/src/Notification/ToastNotification.svelte b/src/Notification/ToastNotification.svelte
index 63da68c0..b8ac4924 100644
--- a/src/Notification/ToastNotification.svelte
+++ b/src/Notification/ToastNotification.svelte
@@ -55,6 +55,9 @@
   let timeoutId = undefined;
 
   function close(closeFromTimeout) {
+    // Clear the timer if the close button was clicked.
+    clearTimeout(timeoutId);
+
     const shouldContinue = dispatch(
       "close",
       { timeout: closeFromTimeout === true },
@@ -66,14 +69,24 @@
   }
 
   onMount(() => {
-    if (timeout) {
-      timeoutId = setTimeout(() => close(true), timeout);
-    }
-
     return () => {
       clearTimeout(timeoutId);
     };
   });
+
+  $: if (typeof window !== "undefined") {
+    /**
+     * Clear the timer if {@link timeout} changes.
+     * If set to `0`, no new timeout is started.
+     * Else, a new timeout is started if {@link open} is not set to `false`.
+     */
+    clearTimeout(timeoutId);
+
+    /** Only start the timer of {@link open} has not been set to `false`. */
+    if (open && timeout) {
+      timeoutId = setTimeout(() => close(true), timeout);
+    }
+  }
 </script>
 
 <!-- svelte-ignore a11y-mouse-events-have-key-events -->