diff --git a/.changeset/nervous-laws-knock.md b/.changeset/nervous-laws-knock.md
new file mode 100644
index 0000000000000..b9b979fb9367a
--- /dev/null
+++ b/.changeset/nervous-laws-knock.md
@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Narrow type of `Params`, as its values cannot be numbers
diff --git a/packages/astro/src/@types/astro.ts b/packages/astro/src/@types/astro.ts
index d24b194c8c6d5..1c362117184ef 100644
--- a/packages/astro/src/@types/astro.ts
+++ b/packages/astro/src/@types/astro.ts
@@ -28,6 +28,10 @@ export type {
 } from '@astrojs/markdown-remark';
 export type { SSRManifest } from '../core/app/types';
 
+type UnionRecord<A extends Record<any, any>, B extends Record<any, any>> = {
+	[K in keyof A | keyof B]: A[K] | B[K];
+};
+
 export interface AstroBuiltinProps {
 	'client:load'?: boolean;
 	'client:idle'?: boolean;
@@ -1047,7 +1051,7 @@ export type GetHydrateCallback = () => Promise<() => void | Promise<void>>;
 	rss(): never;
 }
 
-export type GetStaticPathsItem = { params: Params; props?: Props };
+export type GetStaticPathsItem = { params: UnionRecord<Params, Record<string, number>>; props?: Props };
 export type GetStaticPathsResult = GetStaticPathsItem[];
 export type GetStaticPathsResultKeyed = GetStaticPathsResult & {
 	keyed: Map<string, GetStaticPathsItem>;
@@ -1146,7 +1150,7 @@ export interface Page<T = any> {
 
 export type PaginateFunction = (data: any[], args?: PaginateOptions) => GetStaticPathsResult;
 
-export type Params = Record<string, string | number | undefined>;
+export type Params = Record<string, string | undefined>;
 
 export interface AstroAdapter {
 	name: string;
diff --git a/packages/astro/src/core/routing/params.ts b/packages/astro/src/core/routing/params.ts
index 0b92751708538..6a822861fecf7 100644
--- a/packages/astro/src/core/routing/params.ts
+++ b/packages/astro/src/core/routing/params.ts
@@ -1,4 +1,4 @@
-import type { Params } from '../../@types/astro';
+import type { GetStaticPathsItem, Params } from '../../@types/astro';
 import { validateGetStaticPathsParameter } from './validation.js';
 
 /**
@@ -27,12 +27,12 @@ export function getParams(array: string[]) {
  * values and create a stringified key for the route
  * that can be used to match request routes
  */
-export function stringifyParams(params: Params, routeComponent: string) {
+export function stringifyParams(params: GetStaticPathsItem['params'], routeComponent: string) {
 	// validate parameter values then stringify each value
 	const validatedParams = Object.entries(params).reduce((acc, next) => {
 		validateGetStaticPathsParameter(next, routeComponent);
 		const [key, value] = next;
-		acc[key] = typeof value === 'undefined' ? undefined : `${value}`;
+		acc[key] = value?.toString();
 		return acc;
 	}, {} as Params);