diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 415889c83..d374fbd9e 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -15,9 +15,9 @@ jobs:
         node-version: [16.x, 18.x, 20.x, 21.x]
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - name: use Node.js ${{ matrix.node-version }}
-        uses: actions/setup-node@v2
+        uses: actions/setup-node@v4
         with:
           node-version: ${{ matrix.node-version }}
       - run: npm install
@@ -32,6 +32,6 @@ jobs:
       - run: npm run build
       - run: npm run test-ci
       - name: coveralls
-        uses: coverallsapp/github-action@master
+        uses: coverallsapp/github-action@v2
         with:
           github-token: ${{ secrets.GITHUB_TOKEN }}
diff --git a/.github/workflows/publish.yml b/.github/workflows/publish.yml
index 2da03454b..35bf8ed67 100644
--- a/.github/workflows/publish.yml
+++ b/.github/workflows/publish.yml
@@ -8,21 +8,21 @@ jobs:
   publish-npm:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
-      - uses: actions/setup-node@v2
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
         with:
-          node-version: 14
+          node-version: 18
           registry-url: https://registry.npmjs.org/
       - run: npm install
       - run: git submodule update --init
       - run: npm run test-ci
       - name: Publish beta version to npm
-        if: "github.event.release.prerelease"
+        if: ${{ github.event.release.prerelease }}
         run: npm publish --tag beta
         env:
           NODE_AUTH_TOKEN: ${{ secrets.NPM_TOKEN }}
       - name: Publish to npm
-        if: "!github.event.release.prerelease"
+        if: ${{ !github.event.release.prerelease }}
         run: npm publish
         env:
           NODE_AUTH_TOKEN: ${{ secrets.NPM_TOKEN }}
diff --git a/README.md b/README.md
index c10422e63..d8ee276ce 100644
--- a/README.md
+++ b/README.md
@@ -8,7 +8,7 @@ The fastest JSON validator for Node.js and browser.
 
 Supports JSON Schema draft-04/06/07/2019-09/2020-12 ([draft-04 support](https://ajv.js.org/json-schema.html#draft-04) requires ajv-draft-04 package) and JSON Type Definition [RFC8927](https://datatracker.ietf.org/doc/rfc8927/).
 
-[![build](https://github.com/ajv-validator/ajv/workflows/build/badge.svg)](https://github.com/ajv-validator/ajv/actions?query=workflow%3Abuild)
+[![build](https://github.com/ajv-validator/ajv/actions/workflows/build.yml/badge.svg)](https://github.com/ajv-validator/ajv/actions?query=workflow%3Abuild)
 [![npm](https://img.shields.io/npm/v/ajv.svg)](https://www.npmjs.com/package/ajv)
 [![npm downloads](https://img.shields.io/npm/dm/ajv.svg)](https://www.npmjs.com/package/ajv)
 [![Coverage Status](https://coveralls.io/repos/github/ajv-validator/ajv/badge.svg?branch=master)](https://coveralls.io/github/ajv-validator/ajv?branch=master)
diff --git a/docs/json-schema.md b/docs/json-schema.md
index ac2d82d84..c888c636d 100644
--- a/docs/json-schema.md
+++ b/docs/json-schema.md
@@ -280,6 +280,10 @@ The value of the keyword should be a number. The data to be valid should be a mu
 
 ### `maxLength` / `minLength`
 
+::: warning Grapheme clusters will count as multiple characters
+Certain charsets have characters that are made up of multiple Unicode code points. These [grapheme clusters](https://www.unicode.org/reports/tr29/tr29-17.html#Grapheme_Cluster_Boundaries) are counted as multiple in length calculations.
+:::
+
 The value of the keywords should be a number. The data to be valid should have length satisfying this rule. Unicode pairs are counted as a single character.
 
 **Examples**
diff --git a/lib/vocabularies/discriminator/index.ts b/lib/vocabularies/discriminator/index.ts
index 98f0f8cfb..19ae6049f 100644
--- a/lib/vocabularies/discriminator/index.ts
+++ b/lib/vocabularies/discriminator/index.ts
@@ -3,6 +3,7 @@ import type {KeywordCxt} from "../../compile/validate"
 import {_, getProperty, Name} from "../../compile/codegen"
 import {DiscrError, DiscrErrorObj} from "../discriminator/types"
 import {resolveRef, SchemaEnv} from "../../compile"
+import MissingRefError from "../../compile/ref_error"
 import {schemaHasRulesButRef} from "../../compile/util"
 
 export type DiscriminatorError = DiscrErrorObj<DiscrError.Tag> | DiscrErrorObj<DiscrError.Mapping>
@@ -66,8 +67,10 @@ const def: CodeKeywordDefinition = {
       for (let i = 0; i < oneOf.length; i++) {
         let sch = oneOf[i]
         if (sch?.$ref && !schemaHasRulesButRef(sch, it.self.RULES)) {
-          sch = resolveRef.call(it.self, it.schemaEnv.root, it.baseId, sch?.$ref)
+          const ref = sch.$ref
+          sch = resolveRef.call(it.self, it.schemaEnv.root, it.baseId, ref)
           if (sch instanceof SchemaEnv) sch = sch.schema
+          if (sch === undefined) throw new MissingRefError(it.opts.uriResolver, it.baseId, ref)
         }
         const propSch = sch?.properties?.[tagName]
         if (typeof propSch != "object") {
diff --git a/package.json b/package.json
index d80c51a46..21ac5eed3 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "ajv",
-  "version": "8.12.0",
+  "version": "8.13.0",
   "description": "Another JSON Schema Validator",
   "main": "dist/ajv.js",
   "types": "dist/ajv.d.ts",
@@ -104,7 +104,7 @@
     "rollup-plugin-terser": "^7.0.2",
     "ts-node": "^10.9.2",
     "tsify": "^5.0.4",
-    "typescript": "^4.9.5"
+    "typescript": "5.3.3"
   },
   "collective": {
     "type": "opencollective",
diff --git a/spec/discriminator.spec.ts b/spec/discriminator.spec.ts
index 28ff12146..74ba33ef0 100644
--- a/spec/discriminator.spec.ts
+++ b/spec/discriminator.spec.ts
@@ -159,6 +159,67 @@ describe("discriminator keyword", function () {
     })
   })
 
+  describe("schema with external $refs", () => {
+    const schemas = {
+      main: {
+        type: "object",
+        discriminator: {propertyName: "foo"},
+        required: ["foo"],
+        oneOf: [
+          {
+            $ref: "schema1",
+          },
+          {
+            $ref: "schema2",
+          },
+        ],
+      },
+      schema1: {
+        type: "object",
+        properties: {
+          foo: {const: "x"},
+        },
+      },
+      schema2: {
+        type: "object",
+        properties: {
+          foo: {enum: ["y", "z"]},
+        },
+      },
+    }
+
+    const data = {foo: "x"}
+    const badData = {foo: "w"}
+
+    it("compile should resolve each $ref to a schema that was added with addSchema", () => {
+      const opts = {
+        discriminator: true,
+      }
+      const ajv = new _Ajv(opts)
+      ajv.addSchema(schemas.main, "https://host/main")
+      ajv.addSchema(schemas.schema1, "https://host/schema1")
+      ajv.addSchema(schemas.schema2, "https://host/schema2")
+
+      const validate = ajv.compile({$ref: "https://host/main"})
+      assert.strictEqual(validate(data), true)
+      assert.strictEqual(validate(badData), false)
+    })
+    it("compileAsync should loadSchema each $ref", async () => {
+      const opts = {
+        discriminator: true,
+        loadSchema(url) {
+          if (!url.startsWith("https://host/")) return undefined
+          const name = url.substring("https://host/".length)
+          return schemas[name]
+        },
+      }
+      const ajv = new _Ajv(opts)
+      const validate = await ajv.compileAsync({$ref: "https://host/main"})
+      assert.strictEqual(validate(data), true)
+      assert.strictEqual(validate(badData), false)
+    })
+  })
+
   describe("validation with deeply referenced schemas", () => {
     const schema = [
       {
diff --git a/spec/types/async-validate.spec.ts b/spec/types/async-validate.spec.ts
index 8e3f0588c..83a61417a 100644
--- a/spec/types/async-validate.spec.ts
+++ b/spec/types/async-validate.spec.ts
@@ -109,10 +109,10 @@ describe("$async validation and type guards", () => {
       const data: unknown = {foo: 1}
       let result: boolean | Promise<Foo>
       if ((result = validate(data))) {
-        if (typeof result == "boolean") {
-          data.foo.should.equal(1)
-        } else {
+        if (result instanceof Promise) {
           await result.then((_data) => _data.foo.should.equal(1))
+        } else {
+          should.fail()
         }
       } else {
         should.fail()