diff --git a/tests/utils.ts b/tests/utils.ts
index dc13f31..9aa14d2 100644
--- a/tests/utils.ts
+++ b/tests/utils.ts
@@ -83,11 +83,11 @@ const messagesToReadableStream = (messages: Array<JSONRPCMessage>) => {
  */
 const safeJsonValueArb = fc
   .json()
-  .map((value) => JSON.parse(value.replace('__proto__', 'proto')) as JSONValue)
+  .map((value) => JSON.parse(value.replaceAll('__proto__', 'proto')) as JSONValue)
   .noShrink();
 
 const safeJsonObjectArb = fc.dictionary(
-  fc.string().map((s) => s.replace('__proto__', 'proto')),
+  fc.string().map((s) => s.replaceAll('__proto__', 'proto')),
   safeJsonValueArb,
 ) as fc.Arbitrary<JSONObject>;