diff --git a/.changeset/unlucky-knives-bake.md b/.changeset/unlucky-knives-bake.md
new file mode 100644
index 000000000000..588a1b7f28a7
--- /dev/null
+++ b/.changeset/unlucky-knives-bake.md
@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+fix: correctly show 404 for prerendered dynamic routes when navigating client-side without a root layout server load
diff --git a/packages/kit/src/runtime/client/client.js b/packages/kit/src/runtime/client/client.js
index 80abcfd65742..b68f4bfbade4 100644
--- a/packages/kit/src/runtime/client/client.js
+++ b/packages/kit/src/runtime/client/client.js
@@ -55,6 +55,17 @@ function update_scroll_positions(index) {
 	scroll_positions[index] = scroll_state();
 }
 
+/**
+ * Loads `href` the old-fashioned way, with a full page reload.
+ * Returns a `Promise` that never resolves (to prevent any
+ * subsequent work, e.g. history manipulation, from happening)
+ * @param {URL} url
+ */
+function native_navigation(url) {
+	location.href = url.href;
+	return new Promise(() => {});
+}
+
 /**
  * @param {import('./types.js').SvelteKitApp} app
  * @param {HTMLElement} target
@@ -1196,17 +1207,6 @@ export function create_client(app, target) {
 		return await native_navigation(url);
 	}
 
-	/**
-	 * Loads `href` the old-fashioned way, with a full page reload.
-	 * Returns a `Promise` that never resolves (to prevent any
-	 * subsequent work, e.g. history manipulation, from happening)
-	 * @param {URL} url
-	 */
-	function native_navigation(url) {
-		location.href = url.href;
-		return new Promise(() => {});
-	}
-
 	if (import.meta.hot) {
 		import.meta.hot.on('vite:beforeUpdate', () => {
 			if (current.error) location.reload();
@@ -1842,7 +1842,7 @@ export function create_client(app, target) {
 /**
  * @param {URL} url
  * @param {boolean[]} invalid
- * @returns {Promise<import('types').ServerNodesResponse |import('types').ServerRedirectNode>}
+ * @returns {Promise<import('types').ServerNodesResponse | import('types').ServerRedirectNode>}
  */
 async function load_data(url, invalid) {
 	const data_url = new URL(url);
@@ -1857,13 +1857,19 @@ async function load_data(url, invalid) {
 
 	const res = await native_fetch(data_url.href);
 
+	// if `__data.json` doesn't exist or the server has an internal error,
+	// fallback to native navigation so we avoid parsing the HTML error page as a JSON
+	if (res.headers.get('content-type')?.includes('text/html')) {
+		await native_navigation(url);
+	}
+
 	if (!res.ok) {
 		// error message is a JSON-stringified string which devalue can't handle at the top level
 		// turn it into a HttpError to not call handleError on the client again (was already handled on the server)
 		throw new HttpError(res.status, await res.json());
 	}
 
-	// TODO: fix eslint error
+	// TODO: fix eslint error / figure out if it actually applies to our situation
 	// eslint-disable-next-line
 	return new Promise(async (resolve) => {
 		/**