diff --git a/exercises/practice/hello-world/.meta/instructions.append.md b/exercises/practice/hello-world/.meta/instructions.append.md
new file mode 100644
index 0000000..f6c29a1
--- /dev/null
+++ b/exercises/practice/hello-world/.meta/instructions.append.md
@@ -0,0 +1,9 @@
+# Instructions append
+
+~~~~exercism/caution
+
+Unlike most “Hello World” exercises on Exercism, WebAssembly requires an extra change to the code you are provided with in the start file.
+As well as changing the string itself, you must also change the **length of the greeting** in the function definition.
+See the comment in the starter code for more details.
+
+~~~~
\ No newline at end of file
diff --git a/exercises/practice/hello-world/hello-world.wat b/exercises/practice/hello-world/hello-world.wat
index 0761569..1708562 100644
--- a/exercises/practice/hello-world/hello-world.wat
+++ b/exercises/practice/hello-world/hello-world.wat
@@ -5,6 +5,7 @@
   (data (i32.const 64) "Goodbye, Mars!")
   
   ;; Returns the base offset and length of the greeting
+  ;; The final number (currently “14”) must match the length of the new string.
   (func (export "hello") (result i32 i32)
     (i32.const 64) (i32.const 14)
   )