diff --git a/compiler/rustc_error_codes/src/error_codes/E0756.md b/compiler/rustc_error_codes/src/error_codes/E0756.md
index ffdc421aab584..19d24a76afdda 100644
--- a/compiler/rustc_error_codes/src/error_codes/E0756.md
+++ b/compiler/rustc_error_codes/src/error_codes/E0756.md
@@ -21,6 +21,9 @@ extern "C" {
     #[ffi_const] // ok!
     pub fn strlen(s: *const i8) -> i32;
 }
+
+#[ffi_pure]
+extern "C" pub fn foo() {} // ok!
 # fn main() {}
 ```