diff --git a/compiler/rustc_attr/src/builtin.rs b/compiler/rustc_attr/src/builtin.rs
index 46643df84ccd..6397d4e236a0 100644
--- a/compiler/rustc_attr/src/builtin.rs
+++ b/compiler/rustc_attr/src/builtin.rs
@@ -465,7 +465,7 @@ fn find_stability_generic<'a, I>(
             struct_span_err!(
                 diagnostic,
                 item_sp,
-                E0788,
+                E0789,
                 "`rustc_allowed_through_unstable_modules` attribute must be paired with a `stable` attribute"
             )
             .emit();
diff --git a/compiler/rustc_error_codes/src/error_codes.rs b/compiler/rustc_error_codes/src/error_codes.rs
index 56f29dcc5ce9..977318b85895 100644
--- a/compiler/rustc_error_codes/src/error_codes.rs
+++ b/compiler/rustc_error_codes/src/error_codes.rs
@@ -644,5 +644,5 @@
 //  E0721, // `await` keyword
 //  E0723, // unstable feature in `const` context
 //  E0738, // Removed; errored on `#[track_caller] fn`s in `extern "Rust" { ... }`.
-    E0788, // rustc_allowed_through_unstable_modules without stability attribute
+    E0789, // rustc_allowed_through_unstable_modules without stability attribute
 }
diff --git a/compiler/rustc_middle/src/middle/stability.rs b/compiler/rustc_middle/src/middle/stability.rs
index 9f00c6ac1126..91f6cdd0877e 100644
--- a/compiler/rustc_middle/src/middle/stability.rs
+++ b/compiler/rustc_middle/src/middle/stability.rs
@@ -492,6 +492,8 @@ pub fn check_stability(
     /// If so, and `id` is not `None`, a deprecated lint attached to `id` will be emitted.
     ///
     /// Pass `AllowUnstable::Yes` to `allow_unstable` to force an unstable item to be allowed. Deprecation warnings will be emitted normally.
+    ///
+    /// Returns `true` if item is allowed aka, stable or unstable under an enabled feature.
     pub fn check_stability_allow_unstable(
         self,
         def_id: DefId,
diff --git a/compiler/rustc_passes/src/stability.rs b/compiler/rustc_passes/src/stability.rs
index cf23e0ae5ef2..ef7c3fc0966f 100644
--- a/compiler/rustc_passes/src/stability.rs
+++ b/compiler/rustc_passes/src/stability.rs
@@ -858,7 +858,7 @@ fn visit_path(&mut self, path: &'tcx hir::Path<'tcx>, id: hir::HirId) {
                             } else {
                                 AllowUnstable::No
                             },
-                        )
+                        );
                     }
                 }
             }
diff --git a/src/test/ui-fulldeps/stability-attribute/rustc-encodable-stability.rs b/src/test/ui-fulldeps/rustc-encodable-stability.rs
similarity index 100%
rename from src/test/ui-fulldeps/stability-attribute/rustc-encodable-stability.rs
rename to src/test/ui-fulldeps/rustc-encodable-stability.rs
diff --git a/src/test/ui/stability-attribute/allow-through-unstable-misuse.rs b/src/test/ui/stability-attribute/allow-through-unstable-misuse.rs
deleted file mode 100644
index 7f942309e049..000000000000
--- a/src/test/ui/stability-attribute/allow-through-unstable-misuse.rs
+++ /dev/null
@@ -1,8 +0,0 @@
-#![crate_type = "lib"]
-#![feature(staged_api)]
-#![feature(rustc_attrs)]
-#![stable(feature = "foo", since = "1.0.0")]
-
-#[unstable(feature = "bar", issue = "none")]
-#[rustc_allowed_through_unstable_modules]
-pub struct UnstableType(());
diff --git a/src/test/ui/stability-attribute/allowed-through-unstable.stderr b/src/test/ui/stability-attribute/allowed-through-unstable.stderr
index 70b1dc3010a4..132c00b89b22 100644
--- a/src/test/ui/stability-attribute/allowed-through-unstable.stderr
+++ b/src/test/ui/stability-attribute/allowed-through-unstable.stderr
@@ -1,5 +1,5 @@
 error[E0658]: use of unstable library feature 'unstable_test_feature'
-  --> $DIR/allowed-through-unstable.rs:10:5
+  --> $DIR/allowed-through-unstable.rs:9:5
    |
 LL | use allowed_through_unstable_core::unstable_module::NewStableTraitNotAllowedThroughUnstable;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/src/test/ui/stability-attribute/rustc-encodable-stability.rs b/src/test/ui/stability-attribute/rustc-encodable-stability.rs
deleted file mode 100644
index 18eff27d9a53..000000000000
--- a/src/test/ui/stability-attribute/rustc-encodable-stability.rs
+++ /dev/null
@@ -1,8 +0,0 @@
-// edition:2018
-#![allow(deprecated)]
-extern crate rustc_serialize;
-
-#[derive(RustcDecodable, RustcEncodable)]
-struct ArbitraryTestType(());
-
-fn main() {}
diff --git a/src/tools/tidy/src/error_codes_check.rs b/src/tools/tidy/src/error_codes_check.rs
index e56ce3329cc4..4ffa1fa8b28d 100644
--- a/src/tools/tidy/src/error_codes_check.rs
+++ b/src/tools/tidy/src/error_codes_check.rs
@@ -11,7 +11,7 @@
 // A few of those error codes can't be tested but all the others can and *should* be tested!
 const EXEMPTED_FROM_TEST: &[&str] = &[
     "E0279", "E0313", "E0377", "E0461", "E0462", "E0465", "E0476", "E0490", "E0514", "E0519",
-    "E0523", "E0554", "E0640", "E0717", "E0729",
+    "E0523", "E0554", "E0640", "E0717", "E0729", "E0789",
 ];
 
 // Some error codes don't have any tests apparently...