diff --git a/src/tools/jsondoclint/src/validator.rs b/src/tools/jsondoclint/src/validator.rs
index f1b9c1acbaec0..c6f55410e4437 100644
--- a/src/tools/jsondoclint/src/validator.rs
+++ b/src/tools/jsondoclint/src/validator.rs
@@ -3,14 +3,17 @@ use std::hash::Hash;
 
 use rustdoc_json_types::{
     Constant, Crate, DynTrait, Enum, FnDecl, Function, FunctionPointer, GenericArg, GenericArgs,
-    GenericBound, GenericParamDef, Generics, Id, Impl, Import, ItemEnum, Module, OpaqueTy, Path,
-    Primitive, ProcMacro, Static, Struct, StructKind, Term, Trait, TraitAlias, Type, TypeBinding,
-    TypeBindingKind, Typedef, Union, Variant, VariantKind, WherePredicate,
+    GenericBound, GenericParamDef, Generics, Id, Impl, Import, ItemEnum, ItemSummary, Module,
+    OpaqueTy, Path, Primitive, ProcMacro, Static, Struct, StructKind, Term, Trait, TraitAlias,
+    Type, TypeBinding, TypeBindingKind, Typedef, Union, Variant, VariantKind, WherePredicate,
 };
 use serde_json::Value;
 
 use crate::{item_kind::Kind, json_find, Error, ErrorKind};
 
+// This is a rustc implementation detail that we rely on here
+const LOCAL_CRATE_ID: u32 = 0;
+
 /// The Validator walks over the JSON tree, and ensures it is well formed.
 /// It is made of several parts.
 ///
@@ -53,12 +56,19 @@ impl<'a> Validator<'a> {
     }
 
     pub fn check_crate(&mut self) {
+        // Graph traverse the index
         let root = &self.krate.root;
         self.add_mod_id(root);
         while let Some(id) = set_remove(&mut self.todo) {
             self.seen_ids.insert(id);
             self.check_item(id);
         }
+
+        let root_crate_id = self.krate.index[root].crate_id;
+        assert_eq!(root_crate_id, LOCAL_CRATE_ID, "LOCAL_CRATE_ID is wrong");
+        for (id, item_info) in &self.krate.paths {
+            self.check_item_info(id, item_info);
+        }
     }
 
     fn check_item(&mut self, id: &'a Id) {
@@ -364,6 +374,19 @@ impl<'a> Validator<'a> {
         fp.generic_params.iter().for_each(|gpd| self.check_generic_param_def(gpd));
     }
 
+    fn check_item_info(&mut self, id: &Id, item_info: &ItemSummary) {
+        // FIXME: Their should be a better way to determine if an item is local, rather than relying on `LOCAL_CRATE_ID`,
+        // which encodes rustc implementation details.
+        if item_info.crate_id == LOCAL_CRATE_ID && !self.krate.index.contains_key(id) {
+            self.errs.push(Error {
+                id: id.clone(),
+                kind: ErrorKind::Custom(
+                    "Id for local item in `paths` but not in `index`".to_owned(),
+                ),
+            })
+        }
+    }
+
     fn add_id_checked(&mut self, id: &'a Id, valid: fn(Kind) -> bool, expected: &str) {
         if let Some(kind) = self.kind_of(id) {
             if valid(kind) {
diff --git a/src/tools/jsondoclint/src/validator/tests.rs b/src/tools/jsondoclint/src/validator/tests.rs
index 37b826153efb1..1ef41ff123abf 100644
--- a/src/tools/jsondoclint/src/validator/tests.rs
+++ b/src/tools/jsondoclint/src/validator/tests.rs
@@ -1,6 +1,6 @@
 use std::collections::HashMap;
 
-use rustdoc_json_types::{Crate, Item, Visibility};
+use rustdoc_json_types::{Crate, Item, ItemKind, ItemSummary, Visibility, FORMAT_VERSION};
 
 use crate::json_find::SelectorPart;
 
@@ -64,3 +64,101 @@ fn errors_on_missing_links() {
         }],
     );
 }
+
+// Test we would catch
+// https://github.com/rust-lang/rust/issues/104064#issuecomment-1368589718
+#[test]
+fn errors_on_local_in_paths_and_not_index() {
+    let krate = Crate {
+        root: id("0:0:1572"),
+        crate_version: None,
+        includes_private: false,
+        index: HashMap::from_iter([
+            (
+                id("0:0:1572"),
+                Item {
+                    id: id("0:0:1572"),
+                    crate_id: 0,
+                    name: Some("microcore".to_owned()),
+                    span: None,
+                    visibility: Visibility::Public,
+                    docs: None,
+                    links: HashMap::from_iter([(("prim@i32".to_owned(), id("0:1:1571")))]),
+                    attrs: Vec::new(),
+                    deprecation: None,
+                    inner: ItemEnum::Module(Module {
+                        is_crate: true,
+                        items: vec![id("0:1:717")],
+                        is_stripped: false,
+                    }),
+                },
+            ),
+            (
+                id("0:1:717"),
+                Item {
+                    id: id("0:1:717"),
+                    crate_id: 0,
+                    name: Some("i32".to_owned()),
+                    span: None,
+                    visibility: Visibility::Public,
+                    docs: None,
+                    links: HashMap::default(),
+                    attrs: Vec::new(),
+                    deprecation: None,
+                    inner: ItemEnum::Primitive(Primitive { name: "i32".to_owned(), impls: vec![] }),
+                },
+            ),
+        ]),
+        paths: HashMap::from_iter([(
+            id("0:1:1571"),
+            ItemSummary {
+                crate_id: 0,
+                path: vec!["microcore".to_owned(), "i32".to_owned()],
+                kind: ItemKind::Primitive,
+            },
+        )]),
+        external_crates: HashMap::default(),
+        format_version: rustdoc_json_types::FORMAT_VERSION,
+    };
+
+    check(
+        &krate,
+        &[Error {
+            id: id("0:1:1571"),
+            kind: ErrorKind::Custom("Id for local item in `paths` but not in `index`".to_owned()),
+        }],
+    );
+}
+
+#[test]
+#[should_panic = "LOCAL_CRATE_ID is wrong"]
+fn checks_local_crate_id_is_correct() {
+    let krate = Crate {
+        root: id("root"),
+        crate_version: None,
+        includes_private: false,
+        index: HashMap::from_iter([(
+            id("root"),
+            Item {
+                id: id("root"),
+                crate_id: LOCAL_CRATE_ID.wrapping_add(1),
+                name: Some("irrelavent".to_owned()),
+                span: None,
+                visibility: Visibility::Public,
+                docs: None,
+                links: HashMap::default(),
+                attrs: Vec::new(),
+                deprecation: None,
+                inner: ItemEnum::Module(Module {
+                    is_crate: true,
+                    items: vec![],
+                    is_stripped: false,
+                }),
+            },
+        )]),
+        paths: HashMap::default(),
+        external_crates: HashMap::default(),
+        format_version: FORMAT_VERSION,
+    };
+    check(&krate, &[]);
+}