diff --git a/src/lexer.js b/src/lexer.js
index f5e01c6..4aee529 100755
--- a/src/lexer.js
+++ b/src/lexer.js
@@ -2,17 +2,21 @@ const strictReserved = new Set(['implements', 'interface', 'let', 'package', 'pr
 
 let wasm;
 
+const isLE = new Uint8Array(new Uint16Array([1]).buffer)[0] === 1;
+
 export function parse (source, name = '@') {
   if (!wasm)
     throw new Error('Not initialized');
 
+  const len = source.length + 1;
+
   // need 2 bytes per code point plus analysis space so we double again
-  const extraMem = (wasm.__heap_base.value || wasm.__heap_base) + source.length * 4 - wasm.memory.buffer.byteLength;
+  const extraMem = (wasm.__heap_base.value || wasm.__heap_base) + len * 4 - wasm.memory.buffer.byteLength;
   if (extraMem > 0)
     wasm.memory.grow(Math.ceil(extraMem / 65536));
     
-  const addr = wasm.sa(source.length);
-  copy(source, new Uint16Array(wasm.memory.buffer, addr, source.length + 1));
+  const addr = wasm.sa(len);
+  (isLE ? copyLE : copyBE)(source, new Uint16Array(wasm.memory.buffer, addr, len));
 
   if (!wasm.parseCJS(addr, source.length, 0, 0))
     throw Object.assign(new Error(`Parse error ${name}${wasm.e()}:${source.slice(0, wasm.e()).split('\n').length}:${wasm.e() - source.lastIndexOf('\n', wasm.e() - 1)}`), { idx: wasm.e() });
@@ -29,7 +33,16 @@ export function parse (source, name = '@') {
   return { exports: [...exports], reexports: [...reexports] };
 }
 
-function copy (src, outBuf16) {
+function copyBE (src, outBuf16) {
+  const len = src.length;
+  let i = 0;
+  while (i < len) {
+    const ch = src.charCodeAt(i);
+    outBuf16[i++] = (ch & 0xff) << 8 | (ch & 0xff0) >> 8;
+  }
+}
+
+function copyLE (src, outBuf16) {
   const len = src.length;
   let i = 0;
   while (i < len)