diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index b34a64108e3b4..083e04730bc37 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -236,6 +236,7 @@ symbols! {
         File,
         FileType,
         FmtArgumentsNew,
+        FmtWrite,
         Fn,
         FnMut,
         FnOnce,
diff --git a/library/core/src/fmt/mod.rs b/library/core/src/fmt/mod.rs
index fcd2e52101ff0..0f255e57fe585 100644
--- a/library/core/src/fmt/mod.rs
+++ b/library/core/src/fmt/mod.rs
@@ -115,6 +115,7 @@ pub struct Error;
 /// [`std::io::Write`]: ../../std/io/trait.Write.html
 /// [flushable]: ../../std/io/trait.Write.html#tymethod.flush
 #[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_diagnostic_item = "FmtWrite"]
 pub trait Write {
     /// Writes a string slice into this writer, returning whether the write
     /// succeeded.