diff --git a/src/doc/trpl/ffi.md b/src/doc/trpl/ffi.md
index b4c181b7e72d..640f9cc388ef 100644
--- a/src/doc/trpl/ffi.md
+++ b/src/doc/trpl/ffi.md
@@ -529,6 +529,7 @@ fairly easy, but requires a few things:
 pub extern fn hello_rust() -> *const u8 {
     "Hello, world!\0".as_ptr()
 }
+# fn main() {}
 ```
 
 The `extern` makes this function adhere to the C calling convention, as