diff --git a/js/src/jest/index.ts b/js/src/jest/index.ts
index 1ef8c48aa..9c358d059 100644
--- a/js/src/jest/index.ts
+++ b/js/src/jest/index.ts
@@ -17,7 +17,7 @@ import {
   toBeSemanticCloseTo,
 } from "./matchers.js";
 import { jestAsyncLocalStorageInstance, trackingEnabled } from "./globals.js";
-import expectWithGradedBy from "./vendor/chain.js";
+import { wrapExpect } from "./vendor/chain.js";
 import type { SimpleEvaluator } from "./vendor/gradedBy.js";
 
 declare global {
@@ -339,11 +339,13 @@ const lsTest = Object.assign(wrapTestMethod(test), {
   each: eachMethod,
 });
 
+const wrappedExpect = wrapExpect(expect);
+
 export {
   lsTest as test,
   lsTest as it,
   lsDescribe as describe,
-  expectWithGradedBy as expect,
+  wrappedExpect as expect,
 };
 
 export { type SimpleEvaluator };
diff --git a/js/src/jest/vendor/chain.ts b/js/src/jest/vendor/chain.ts
index 84699130b..a15bac8f3 100644
--- a/js/src/jest/vendor/chain.ts
+++ b/js/src/jest/vendor/chain.ts
@@ -1,7 +1,7 @@
 /**
  * Adapted from https://github.com/mattphillips/jest-chain/blob/main/src/chain.js
  */
-
+import { expect } from "@jest/globals";
 import { gradedBy, SimpleEvaluator } from "./gradedBy.js";
 
 class JestAssertionError extends Error {
@@ -58,22 +58,39 @@ const addGradedBy = (
   originalArgs: any[],
   staticPath: string[] = []
 ) => {
+  let spreadMatchers = { ...matchers };
+  // Handle Bun, which uses a class
+  if (Object.keys(matchers).length === 0) {
+    const prototypeProps = Object.getOwnPropertyNames(
+      Object.getPrototypeOf(matchers)
+    );
+    spreadMatchers = Object.fromEntries(
+      prototypeProps.map((prop) => {
+        try {
+          return [prop, (matchers as any)[prop]];
+        } catch (e) {
+          // Ignore bizarre Bun bug
+          return [];
+        }
+      })
+    ) as any;
+  }
   return Object.assign({}, matchers, {
     gradedBy: function (evaluator: SimpleEvaluator) {
       const mappedMatchers: any = _wrapMatchers(
-        matchers,
+        spreadMatchers,
         evaluator,
         originalArgs
       );
       // .not etc.
-      const staticMatchers = Object.keys(matchers)
+      const staticMatchers = Object.keys(spreadMatchers)
         .filter((name) => typeof (matchers as any)[name] !== "function")
         .map((name) => {
           return {
             [name]: Object.assign(
               {},
               ..._wrapMatchers(
-                matchers,
+                spreadMatchers,
                 evaluator,
                 originalArgs,
                 staticPath.concat(name)
@@ -86,7 +103,7 @@ const addGradedBy = (
   });
 };
 
-export default function expectWithGradedBy(expect: any) {
+export function wrapExpect(expect: any) {
   // proxy the expect function
   const expectProxy = Object.assign(
     (...args: any[]) => addGradedBy(expect(...args), args), // partially apply expect to get all matchers and chain them
@@ -96,4 +113,4 @@ export default function expectWithGradedBy(expect: any) {
   return expectProxy;
 }
 
-(globalThis as any).expect = expectWithGradedBy((globalThis as any).expect);
+(globalThis as any).expect = wrapExpect((globalThis as any).expect);