diff --git a/test/harness/async_index.js b/test/harness/async_index.js
index 5812f347fd..8a01b21211 100644
--- a/test/harness/async_index.js
+++ b/test/harness/async_index.js
@@ -52,6 +52,15 @@ const EXPECT_INVALID = false;
 
 /* DATA **********************************************************************/
 
+let hostrefs = {};
+let hostsym = Symbol("hostref");
+function hostref(s) {
+  if (! (s in hostrefs)) hostrefs[s] = {[hostsym]: s};
+  return hostrefs[s];
+}
+function eq_ref(x, y) {
+  return x === y ? 1 : 0;
+}
 let externrefs = {};
 let externsym = Symbol("externref");
 function externref(s) {
@@ -86,6 +95,8 @@ function reinitializeRegistry() {
 
   chain = chain.then(_ => {
     let spectest = {
+      hostref: hostref,
+      eq_ref: eq_ref,
       externref: externref,
       is_externref: is_externref,
       is_funcref: is_funcref,
@@ -182,22 +193,22 @@ function assert_invalid_custom(bytes) {
 
 const assert_malformed_custom = assert_invalid_custom;
 
-function instance(bytes, imports, valid = true) {
+function instance(module, imports, valid = true) {
   const test = valid
     ? "Test that WebAssembly instantiation succeeds"
     : "Test that WebAssembly instantiation fails";
   const loc = new Error().stack.toString().replace("Error", "");
-  chain = Promise.all([imports, chain])
+  chain = Promise.all([module, imports, chain])
     .then(values => {
-      let imports = values[0] ? values[0] : registry;
-      return WebAssembly.instantiate(binary(bytes), imports);
+      let imports = values[1] ? values[1] : registry;
+      return WebAssembly.instantiate(values[0], imports);
     })
     .then(
-      pair => {
+      inst => {
         uniqueTest(_ => {
           assert_true(valid, loc);
         }, test);
-        return pair.instance;
+        return inst;
       },
       error => {
         uniqueTest(_ => {
diff --git a/test/harness/sync_index.js b/test/harness/sync_index.js
index 069c97dff2..5c4549be2e 100644
--- a/test/harness/sync_index.js
+++ b/test/harness/sync_index.js
@@ -66,6 +66,15 @@ const EXPECT_INVALID = false;
 
 /* DATA **********************************************************************/
 
+let hostrefs = {};
+let hostsym = Symbol("hostref");
+function hostref(s) {
+  if (! (s in hostrefs)) hostrefs[s] = {[hostsym]: s};
+  return hostrefs[s];
+}
+function eq_ref(x, y) {
+  return x === y ? 1 : 0;
+}
 let externrefs = {};
 let externsym = Symbol("externref");
 function externref(s) {
@@ -96,6 +105,8 @@ function reinitializeRegistry() {
         return;
 
     let spectest = {
+        hostref: hostref,
+        eq_ref: eq_ref,
         externref: externref,
         is_externref: is_externref,
         is_funcref: is_funcref,
@@ -203,7 +214,7 @@ function assert_invalid_custom(bytes) {
 
 const assert_malformed_custom = assert_invalid_custom;
 
-function instance(bytes, imports = registry, valid = true) {
+function instance(mod, imports = registry, valid = true) {
     if (imports instanceof Result) {
         if (imports.isError())
             return imports;
@@ -212,10 +223,9 @@ function instance(bytes, imports = registry, valid = true) {
 
     let err = null;
 
-    let m, i;
+    let i;
     try {
-        let m = module(bytes);
-        i = new WebAssembly.Instance(m, imports);
+        i = new WebAssembly.Instance(mod, imports);
     } catch(e) {
         err = e;
     }