diff --git a/src/librustc_typeck/diagnostics.rs b/src/librustc_typeck/diagnostics.rs
index c2ce16b02566..694c633f116f 100644
--- a/src/librustc_typeck/diagnostics.rs
+++ b/src/librustc_typeck/diagnostics.rs
@@ -1533,7 +1533,7 @@ For information on the design of the orphan rules, see [RFC 1023].
 [RFC 1023]: https://github.com/rust-lang/rfcs/pull/1023
 "##,
 
-EO118: r##"
+E0118: r##"
 Rust can't find a base type for an implementation you are providing, or the type
 cannot have an implementation. For example, a typedef can't have an implementation,
 since it isn't its own type (this was done in PR #6087):