diff --git a/lib/binding_web/binding.js b/lib/binding_web/binding.js
index 5aa116fa..027a0b89 100644
--- a/lib/binding_web/binding.js
+++ b/lib/binding_web/binding.js
@@ -27,6 +27,10 @@ class Parser {
   }
 
   constructor() {
+    if (TRANSFER_BUFFER == null) {
+      throw new Error('You must first call Parser.init() and wait for it to resolve.');
+    }
+
     C._ts_parser_new_wasm();
     this[0] = getValue(TRANSFER_BUFFER, 'i32');
     this[1] = getValue(TRANSFER_BUFFER + SIZE_OF_INT, 'i32');