diff --git a/src/librustdoc/clean/inline.rs b/src/librustdoc/clean/inline.rs
index d1601272af759..04559bd67bf6d 100644
--- a/src/librustdoc/clean/inline.rs
+++ b/src/librustdoc/clean/inline.rs
@@ -13,6 +13,7 @@ use rustc_hir::def_id::DefId;
 use rustc_hir::Mutability;
 use rustc_metadata::creader::{CStore, LoadedMacro};
 use rustc_middle::ty::{self, TyCtxt};
+use rustc_span::def_id::LOCAL_CRATE;
 use rustc_span::hygiene::MacroKind;
 use rustc_span::symbol::{kw, sym, Symbol};
 
@@ -378,20 +379,32 @@ pub(crate) fn build_impl(
     let tcx = cx.tcx;
     let associated_trait = tcx.impl_trait_ref(did);
 
+    // Do not inline compiler-internal items unless we're a compiler-internal crate.
+    let is_compiler_internal = |did| {
+        if let Some(stab) = tcx.lookup_stability(did) {
+            stab.is_unstable() && stab.feature == sym::rustc_private
+        } else {
+            false
+        }
+    };
+    let document_compiler_internal = is_compiler_internal(LOCAL_CRATE.as_def_id());
+    let is_directly_public = |cx: &mut DocContext<'_>, did| {
+        if !cx.cache.effective_visibilities.is_directly_public(tcx, did) {
+            return false;
+        }
+        if !document_compiler_internal && is_compiler_internal(did) {
+            return false;
+        }
+        true
+    };
+
     // Only inline impl if the implemented trait is
     // reachable in rustdoc generated documentation
     if !did.is_local() {
         if let Some(traitref) = associated_trait {
-            let did = traitref.def_id;
-            if !cx.cache.effective_visibilities.is_directly_public(tcx, did) {
+            if !is_directly_public(cx, traitref.def_id) {
                 return;
             }
-
-            if let Some(stab) = tcx.lookup_stability(did) {
-                if stab.is_unstable() && stab.feature == sym::rustc_private {
-                    return;
-                }
-            }
         }
     }
 
@@ -412,15 +425,9 @@ pub(crate) fn build_impl(
     // reachable in rustdoc generated documentation
     if !did.is_local() {
         if let Some(did) = for_.def_id(&cx.cache) {
-            if !cx.cache.effective_visibilities.is_directly_public(tcx, did) {
+            if !is_directly_public(cx, did) {
                 return;
             }
-
-            if let Some(stab) = tcx.lookup_stability(did) {
-                if stab.is_unstable() && stab.feature == sym::rustc_private {
-                    return;
-                }
-            }
         }
     }
 
diff --git a/src/test/rustdoc/auxiliary/issue-106421-force-unstable.rs b/src/test/rustdoc/auxiliary/issue-106421-force-unstable.rs
new file mode 100644
index 0000000000000..d8b9abfa2c2a7
--- /dev/null
+++ b/src/test/rustdoc/auxiliary/issue-106421-force-unstable.rs
@@ -0,0 +1,9 @@
+// compile-flags: -Zforce-unstable-if-unmarked
+#![crate_name="foo"]
+pub struct FatalError;
+
+impl FatalError {
+    pub fn raise(self) -> ! {
+        loop {}
+    }
+}
diff --git a/src/test/rustdoc/issue-106421-not-internal.rs b/src/test/rustdoc/issue-106421-not-internal.rs
new file mode 100644
index 0000000000000..1477b7b5d2a06
--- /dev/null
+++ b/src/test/rustdoc/issue-106421-not-internal.rs
@@ -0,0 +1,8 @@
+// aux-build:issue-106421-force-unstable.rs
+// ignore-cross-compile
+// This is the version where a non-compiler-internal crate inlines a compiler-internal one.
+// In this case, the item shouldn't be documented, because regular users can't get at it.
+extern crate foo;
+
+// @!has issue_106421_not_internal/struct.FatalError.html '//*[@id="method.raise"]' 'fn raise'
+pub use foo::FatalError;
diff --git a/src/test/rustdoc/issue-106421.rs b/src/test/rustdoc/issue-106421.rs
new file mode 100644
index 0000000000000..7059f57ff5031
--- /dev/null
+++ b/src/test/rustdoc/issue-106421.rs
@@ -0,0 +1,8 @@
+// aux-build:issue-106421-force-unstable.rs
+// ignore-cross-compile
+// compile-flags: -Zforce-unstable-if-unmarked
+
+extern crate foo;
+
+// @has issue_106421/struct.FatalError.html '//*[@id="method.raise"]' 'fn raise'
+pub use foo::FatalError;