diff --git a/packages/wasm-crypto/src/js/bridge.js b/packages/wasm-crypto/src/js/bridge.js
index caa951ab..43df44f7 100644
--- a/packages/wasm-crypto/src/js/bridge.js
+++ b/packages/wasm-crypto/src/js/bridge.js
@@ -9,7 +9,7 @@ let wasm;
 let cachegetInt32 = null;
 let cachegetUint8 = null;
 
-async function initWasm (wasmBytes, asmFallback, wbg) {
+async function initWasm (wasmBytes, asmFn, wbg) {
   try {
     assert(typeof WebAssembly !== 'undefined', 'WebAssembly is not available in your environment');
 
@@ -18,8 +18,8 @@ async function initWasm (wasmBytes, asmFallback, wbg) {
     wasm = source.instance.exports;
   } catch (error) {
     // if we have a valid supplied asm.js, return that
-    if (asmFallback && asmFallback.ext_blake2b) {
-      wasm = asmFallback;
+    if (asmFn) {
+      wasm = asmFn(wbg);
     } else {
       console.error(`ERROR: Unable to initialize ${pkg.name} ${pkg.version}`);
       console.error(error);
diff --git a/packages/wasm-crypto/src/wasm/asm.js b/packages/wasm-crypto/src/wasm/asm.js
index 08ff71d8..b134a071 100644
--- a/packages/wasm-crypto/src/wasm/asm.js
+++ b/packages/wasm-crypto/src/wasm/asm.js
@@ -3,4 +3,4 @@
 
 // Stub replaced at build time
 
-module.exports = {};
+module.exports = null;
diff --git a/scripts/build-package.sh b/scripts/build-package.sh
index 03e6bc40..6152c9a0 100755
--- a/scripts/build-package.sh
+++ b/scripts/build-package.sh
@@ -41,8 +41,7 @@ echo "*** Building asm.js version"
 
 # cleanup the generated asm, converting to cjs
 sed -i -e '/import {/d' $ASM
-echo "const imports = require('../js/imports');
-$(cat $ASM)" > $ASM
-sed -i -e 's/{abort.*},memasmFunc/imports, memasmFunc/g' $ASM
-sed -i -e 's/export var /module\.exports\./g' $ASM
+sed -i -e '/export var /d' $ASM
+sed -i -e 's/{abort.*},memasmFunc/wbg, memasmFunc/g' $ASM
+sed -i -e 's/var retasmFunc = /module.exports = (wbg) => /' $ASM
 rm -rf build/wasm/*-e