diff --git a/packages/svelte/src/internal/client/render.js b/packages/svelte/src/internal/client/render.js
index 534d386ef1..40307fb980 100644
--- a/packages/svelte/src/internal/client/render.js
+++ b/packages/svelte/src/internal/client/render.js
@@ -322,8 +322,11 @@ export function unmount(component) {
  * @returns {Record<string, any>}
  */
 export function sanitize_slots(props) {
-	const sanitized = { ...props.$$slots };
-	if (props.children) sanitized.default = props.children;
+	/** @type {Record<string, boolean>} */
+	const sanitized = {};
+	for (const key in props.$$slots) {
+		sanitized[key] = true;
+	}
 	return sanitized;
 }
 
diff --git a/packages/svelte/src/internal/server/index.js b/packages/svelte/src/internal/server/index.js
index cd5d563545..2d8632063d 100644
--- a/packages/svelte/src/internal/server/index.js
+++ b/packages/svelte/src/internal/server/index.js
@@ -555,8 +555,11 @@ export function sanitize_props(props) {
  * @returns {Record<string, any>}
  */
 export function sanitize_slots(props) {
-	const sanitized = { ...props.$$slots };
-	if (props.children) sanitized.default = props.children;
+	/** @type {Record<string, boolean>} */
+	const sanitized = {};
+	for (const key in props.$$slots) {
+		sanitized[key] = true;
+	}
 	return sanitized;
 }