diff --git a/lib/vocabularies/jtd/properties.ts b/lib/vocabularies/jtd/properties.ts
index 1ef172b5d..b51256d60 100644
--- a/lib/vocabularies/jtd/properties.ts
+++ b/lib/vocabularies/jtd/properties.ts
@@ -2,7 +2,7 @@ import type {CodeKeywordDefinition} from "../../types"
 import type KeywordCxt from "../../compile/context"
 import {propertyInData, allSchemaProperties, isOwnProperty} from "../code"
 import {alwaysValidSchema, schemaRefOrVal} from "../../compile/util"
-import {_, and, Code, Name} from "../../compile/codegen"
+import {_, and, not, Code, Name} from "../../compile/codegen"
 import {checkMetadata} from "./metadata"
 import {checkNullableObject} from "./nullable"
 
@@ -116,7 +116,7 @@ export function validateProperties(cxt: KeywordCxt): void {
     if (props.length > 8) {
       // TODO maybe an option instead of hard-coded 8?
       const propsSchema = schemaRefOrVal(it, parentSchema[keyword], keyword)
-      additional = isOwnProperty(gen, propsSchema as Code, key)
+      additional = not(isOwnProperty(gen, propsSchema as Code, key))
     } else if (props.length) {
       additional = and(...props.map((p) => _`${key} !== ${p}`))
     } else {
diff --git a/spec/issues/1501_jtd_many_properties.spec.ts b/spec/issues/1501_jtd_many_properties.spec.ts
new file mode 100644
index 000000000..20e24b76e
--- /dev/null
+++ b/spec/issues/1501_jtd_many_properties.spec.ts
@@ -0,0 +1,27 @@
+import type Ajv from "../.."
+import _Ajv from "../ajv_jtd"
+import * as assert from "assert"
+
+const PROP_COUNT = 10
+
+describe("schema with many properties", () => {
+  let ajv: Ajv
+  const schema = {properties: {}}
+  const data = {}
+  const invalidData = {}
+
+  before(() => {
+    ajv = new _Ajv()
+    for (let i = 0; i < PROP_COUNT; i++) {
+      const prop = `prop${i}`
+      schema.properties[prop] = {type: "uint16"}
+      data[prop] = i
+      invalidData[prop] = -i
+    }
+  })
+
+  it("should correctly compile reference to schema", () => {
+    assert.strictEqual(ajv.validate(schema, data), true)
+    assert.strictEqual(ajv.validate(schema, invalidData), false)
+  })
+})