diff --git a/lib/core.ts b/lib/core.ts
index 172a63117..32666bd44 100644
--- a/lib/core.ts
+++ b/lib/core.ts
@@ -298,10 +298,10 @@ export default class Ajv {
   // AnySchema will be compiled and cached using schema itself as a key for Map
   validate(schema: Schema | string, data: unknown): boolean
   validate(schemaKeyRef: AnySchema | string, data: unknown): boolean | Promise<unknown>
-  validate<T>(
-    schema: Schema | JTDSchemaType<T> | JSONSchemaType<T> | string,
-    data: unknown
-  ): data is T
+  validate<T>(schema: Schema | JSONSchemaType<T> | string, data: unknown): data is T
+  // This is separated to help typescript with inference
+  // eslint-disable-next-line @typescript-eslint/unified-signatures
+  validate<T>(schema: JTDSchemaType<T>, data: unknown): data is T
   validate<T>(schema: AsyncSchema, data: unknown | T): Promise<T>
   validate<T>(schemaKeyRef: AnySchema | string, data: unknown): data is T | Promise<T>
   validate<T>(
@@ -323,10 +323,10 @@ export default class Ajv {
 
   // Create validation function for passed schema
   // _meta: true if schema is a meta-schema. Used internally to compile meta schemas of user-defined keywords.
-  compile<T = unknown>(
-    schema: Schema | JTDSchemaType<T> | JSONSchemaType<T>,
-    _meta?: boolean
-  ): ValidateFunction<T>
+  compile<T = unknown>(schema: Schema | JSONSchemaType<T>, _meta?: boolean): ValidateFunction<T>
+  // This is separated to help typescript with inference
+  // eslint-disable-next-line @typescript-eslint/unified-signatures
+  compile<T = unknown>(schema: JTDSchemaType<T>, _meta?: boolean): ValidateFunction<T>
   compile<T = unknown>(schema: AsyncSchema, _meta?: boolean): AsyncValidateFunction<T>
   compile<T = unknown>(schema: AnySchema, _meta?: boolean): AnyValidateFunction<T>
   compile<T = unknown>(schema: AnySchema, _meta?: boolean): AnyValidateFunction<T> {
diff --git a/package.json b/package.json
index e8071d67f..f70790479 100644
--- a/package.json
+++ b/package.json
@@ -96,7 +96,7 @@
     "terser": "^5.2.1",
     "ts-node": "^9.0.0",
     "tsify": "^5.0.2",
-    "typescript": "^4.0.0"
+    "typescript": "^4.2.0"
   },
   "collective": {
     "type": "opencollective",
diff --git a/spec/types/jtd-schema.spec.ts b/spec/types/jtd-schema.spec.ts
index a6f3c3dc3..60e3c1662 100644
--- a/spec/types/jtd-schema.spec.ts
+++ b/spec/types/jtd-schema.spec.ts
@@ -30,14 +30,14 @@ const mySchema: JTDSchemaType<MyData> = {
 describe("JTDSchemaType", () => {
   it("validation should prove the data type", () => {
     const ajv = new _Ajv()
-    const validate = ajv.compile<MyData>(mySchema)
+    const validate = ajv.compile(mySchema)
     const validData: unknown = {type: "a", a: 1}
     if (validate(validData) && validData.type === "a") {
       validData.a.should.equal(1)
     }
     should.not.exist(validate.errors)
 
-    if (ajv.validate<MyData>(mySchema, validData) && validData.type === "a") {
+    if (ajv.validate(mySchema, validData) && validData.type === "a") {
       validData.a.should.equal(1)
     }
     should.not.exist(ajv.errors)