diff --git a/packages/environment/src/filters.ts b/packages/environment/src/filters.ts
index d228407..6368ce9 100644
--- a/packages/environment/src/filters.ts
+++ b/packages/environment/src/filters.ts
@@ -1478,7 +1478,10 @@ export const rejectattr: SelectReject = nunjucksFunction(["value"], {
   } else throw new Error("unreachable");
 });
 
-export function tojson(o: unknown, indent = 0): string {
+export const tojson = nunjucksFunction(["o", "indent"])(function tojson(
+  o: unknown,
+  indent: number = 0,
+): string {
   if (o === undefined) {
     return "undefined";
   }
@@ -1495,7 +1498,7 @@ export function tojson(o: unknown, indent = 0): string {
       .replace(/&/g, "\\u0026")
       .replace(/'/g, "\\u0027"),
   );
-}
+});
 
 export default {
   abs,
diff --git a/test/filters.test.ts b/test/filters.test.ts
index c2d3712..eda7743 100644
--- a/test/filters.test.ts
+++ b/test/filters.test.ts
@@ -993,7 +993,12 @@ describe("filters", () => {
     });
 
     it("indent: 2", () => {
-      const tmpl = env.fromString("{{ x | tojson(2) }}");
+      let tmpl = env.fromString("{{ x | tojson(2) }}");
+      expect(tmpl.render({ x: { foo: "bar" } })).toBe('{\n  "foo": "bar"\n}');
+      expect(tmpl.render({ x: ["foo", "bar"] })).toBe(
+        '[\n  "foo",\n  "bar"\n]',
+      );
+      tmpl = env.fromString("{{ x | tojson(indent=2) }}");
       expect(tmpl.render({ x: { foo: "bar" } })).toBe('{\n  "foo": "bar"\n}');
       expect(tmpl.render({ x: ["foo", "bar"] })).toBe(
         '[\n  "foo",\n  "bar"\n]',