diff --git a/src/librustc_error_codes/error_codes/E0751.md b/src/librustc_error_codes/error_codes/E0751.md
index 809b888d92ac3..8794f7868f302 100644
--- a/src/librustc_error_codes/error_codes/E0751.md
+++ b/src/librustc_error_codes/error_codes/E0751.md
@@ -5,8 +5,8 @@ Erroneous code example:
 ```compile_fail,E0751
 trait MyTrait {}
 impl MyTrait for i32 { }
-impl !MyTrait for i32 { }
+impl !MyTrait for i32 { } // error!
 ```
 
-Negative implementations are a promise that the trait will never be
-implemented for the given types.
+Negative implementations are a promise that the trait will never be implemented
+for the given types. Therefore, both cannot exists at the same time.