diff --git a/src/librustc_error_codes/error_codes/E0750.md b/src/librustc_error_codes/error_codes/E0750.md
index e0cf56f716f9d..905e852f8d579 100644
--- a/src/librustc_error_codes/error_codes/E0750.md
+++ b/src/librustc_error_codes/error_codes/E0750.md
@@ -1,4 +1,18 @@
-Negative impls cannot be default impls. A default impl supplies
-default values for the items within to be used by other impls, whereas
-a negative impl declares that there are no other impls. These don't
-make sense to combine.
+A negative impl was made default impl.
+
+Erroneous code example:
+
+```compile_fail,E0750
+# #![feature(negative_impls)]
+# #![feature(specialization)]
+trait MyTrait {
+    type Foo;
+}
+
+default impl !MyTrait for u32 {} // error!
+# fn main() {}
+```
+
+Negative impls cannot be default impls. A default impl supplies default values
+for the items within to be used by other impls, whereas a negative impl declares
+that there are no other impls. Combining it does not make sense.
diff --git a/src/tools/tidy/src/error_codes_check.rs b/src/tools/tidy/src/error_codes_check.rs
index 51f135d376161..9c36d853ef78d 100644
--- a/src/tools/tidy/src/error_codes_check.rs
+++ b/src/tools/tidy/src/error_codes_check.rs
@@ -16,8 +16,7 @@ const EXEMPTED_FROM_TEST: &[&str] = &[
 ];
 
 // Some error codes don't have any tests apparently...
-const IGNORE_EXPLANATION_CHECK: &[&str] =
-    &["E0570", "E0601", "E0602", "E0639", "E0729", "E0749", "E0750"];
+const IGNORE_EXPLANATION_CHECK: &[&str] = &["E0570", "E0601", "E0602", "E0639", "E0729", "E0749"];
 
 fn check_error_code_explanation(
     f: &str,