diff --git a/WebAssembly.md b/WebAssembly.md
index 029edbe0..0815078a 100644
--- a/WebAssembly.md
+++ b/WebAssembly.md
@@ -6,6 +6,13 @@ WebAssembly is described on its [home page](https://webassembly.org) as:
 
 This page will be updated over time with more information relevant to Go's support for WebAssembly.
 
+# Prerequisite 
+
+Note, if you ever set the `GOROOT` environment variable to an old Go SDK path, please remove this environment variable. This environment variable is not needed at more. Otherwise, the `go build` command below will report error: ```
+go tool compile: exit status 2
+compile: unknown architecture "wasm"
+```
+
 # Example
 
 To compile the basic Go program for the web: