diff --git a/shim.ts b/shim.ts
index 4414c14..8feb9c8 100644
--- a/shim.ts
+++ b/shim.ts
@@ -25,12 +25,12 @@ DataView.prototype.readU32 = function () {
 DataView.prototype.readU64 = function () {
   return this.getUint64(0);
 };
-const isDataView = (x: DataView | number[]): x is DataView => {
-  return x instanceof DataView;
+const isU8Array = (x: Uint8Array | number[]): x is Uint8Array => {
+  return x instanceof Uint8Array;
 };
 
 DataView.prototype.writeByteArray = function (arr) {
-  const len = isDataView(arr) ? arr.byteLength : arr.length;
+  const len = isU8Array(arr) ? arr.byteLength : arr.length;
   for (let i = 0; i < len; i++) {
     this.setUint8(i, arr[i]);
   }
@@ -45,7 +45,8 @@ DataView.prototype.readByteArray = function (len) {
 
 const Memory = {
   alloc: (len: number) => new DataView(new ArrayBuffer(len + 1)),
-  copy: (outbuf: DataView, inbuf: DataView, len: number) => outbuf.writeByteArray(inbuf.readByteArray(len)),
+  copy: (outbuf: DataView, inbuf: DataView, len: number) =>
+    outbuf.writeByteArray(new Uint8Array(inbuf.readByteArray(len).buffer)),
 };
 
 declare global {
@@ -56,7 +57,7 @@ declare global {
     readU32(): undefined;
     readU64(): undefined;
     readU8(): undefined;
-    writeByteArray(arr: DataView | number[]): undefined;
+    writeByteArray(arr: Uint8Array | number[]): undefined;
     writeU16(n: number): undefined;
     writeU32(n: number): undefined;
     writeU64(n: number): undefined;