diff --git a/src/doc/book/no-stdlib.md b/src/doc/book/no-stdlib.md
index 610940cde95e6..43bd0507ebbb6 100644
--- a/src/doc/book/no-stdlib.md
+++ b/src/doc/book/no-stdlib.md
@@ -38,7 +38,7 @@ fn start(_argc: isize, _argv: *const *const u8) -> isize {
 // for a bare-bones hello world. These are normally
 // provided by libstd.
 #[lang = "eh_personality"] extern fn eh_personality() {}
-#[lang = "panic_fmt"] fn panic_fmt() -> ! { loop {} }
+#[lang = "panic_fmt"] extern fn panic_fmt() -> ! { loop {} }
 # #[lang = "eh_unwind_resume"] extern fn rust_eh_unwind_resume() {}
 # #[no_mangle] pub extern fn rust_eh_register_frames () {}
 # #[no_mangle] pub extern fn rust_eh_unregister_frames () {}
@@ -65,7 +65,7 @@ pub extern fn main(argc: i32, argv: *const *const u8) -> i32 {
 }
 
 #[lang = "eh_personality"] extern fn eh_personality() {}
-#[lang = "panic_fmt"] fn panic_fmt() -> ! { loop {} }
+#[lang = "panic_fmt"] extern fn panic_fmt() -> ! { loop {} }
 # #[lang = "eh_unwind_resume"] extern fn rust_eh_unwind_resume() {}
 # #[no_mangle] pub extern fn rust_eh_register_frames () {}
 # #[no_mangle] pub extern fn rust_eh_unregister_frames () {}