diff --git a/types/qs/index.d.ts b/types/qs/index.d.ts
index 506aae88191c60..f833cf3fe914fc 100644
--- a/types/qs/index.d.ts
+++ b/types/qs/index.d.ts
@@ -2,8 +2,8 @@ export = QueryString;
 export as namespace qs;
 
 declare namespace QueryString {
-    type defaultEncoder = (str: any, defaultEncoder?: any, charset?: string) => string;
-    type defaultDecoder = (str: string, decoder?: any, charset?: string) => string;
+    type defaultEncoder = (str: unknown, defaultEncoder?: unknown, charset?: string) => string;
+    type defaultDecoder = (str: string, decoder?: unknown, charset?: string) => string;
 
     type BooleanOptional = boolean | undefined;
 
diff --git a/types/three/src/math/Matrix2.d.ts b/types/three/src/math/Matrix2.d.ts
index 93947447d7c9b1..40ed4c8aac3456 100644
--- a/types/three/src/math/Matrix2.d.ts
+++ b/types/three/src/math/Matrix2.d.ts
@@ -12,7 +12,7 @@ export type Matrix2Tuple = [
  * const m = new Matrix2();
  */
 export class Matrix2 {
-    static readonly isMatrix2: boolean;
+    readonly isMatrix2: true;
 
     /**
      * A {@link https://en.wikipedia.org/wiki/Row-_and_column-major_order column-major} list of matrix values.
diff --git a/types/three/src/math/Matrix3.d.ts b/types/three/src/math/Matrix3.d.ts
index 2b601198a100cf..0b593fcb81193f 100644
--- a/types/three/src/math/Matrix3.d.ts
+++ b/types/three/src/math/Matrix3.d.ts
@@ -17,7 +17,7 @@ export type Matrix3Tuple = [
 ];
 
 export class Matrix3 {
-    static readonly isMatrix3: boolean;
+    readonly isMatrix3: true;
 
     /**
      * Array with matrix values.
diff --git a/types/three/src/math/Matrix4.d.ts b/types/three/src/math/Matrix4.d.ts
index e624acdf507461..458d7e4d7b2d36 100644
--- a/types/three/src/math/Matrix4.d.ts
+++ b/types/three/src/math/Matrix4.d.ts
@@ -42,7 +42,7 @@ export type Matrix4Tuple = [
  * m.multiply( m3 );
  */
 export class Matrix4 {
-    static readonly isMatrix4: boolean;
+    readonly isMatrix4: true;
 
     /**
      * Array with matrix values.
diff --git a/types/three/src/math/Vector2.d.ts b/types/three/src/math/Vector2.d.ts
index 7ca5092b85ae95..fd2a84a1d7c756 100644
--- a/types/three/src/math/Vector2.d.ts
+++ b/types/three/src/math/Vector2.d.ts
@@ -12,8 +12,6 @@ export interface Vector2Like {
  * 2D vector.
  */
 export class Vector2 {
-    static readonly isVector2: boolean;
-
     constructor(x?: number, y?: number);
 
     /**
@@ -27,6 +25,7 @@ export class Vector2 {
     y: number;
     width: number;
     height: number;
+    readonly isVector2: true;
 
     /**
      * Sets value of this vector.
diff --git a/types/three/src/math/Vector3.d.ts b/types/three/src/math/Vector3.d.ts
index 6c77a30a167ffc..43dc5629b55127 100644
--- a/types/three/src/math/Vector3.d.ts
+++ b/types/three/src/math/Vector3.d.ts
@@ -29,8 +29,6 @@ export interface Vector3Like {
  * c.crossVectors( a, b );
  */
 export class Vector3 {
-    static readonly isVector3: boolean;
-
     constructor(x?: number, y?: number, z?: number);
 
     /**
@@ -47,6 +45,7 @@ export class Vector3 {
      * @default 0
      */
     z: number;
+    readonly isVector3: true;
 
     /**
      * Sets value of this vector.
diff --git a/types/three/src/math/Vector4.d.ts b/types/three/src/math/Vector4.d.ts
index d04e34630b1859..2e0813d26aecde 100644
--- a/types/three/src/math/Vector4.d.ts
+++ b/types/three/src/math/Vector4.d.ts
@@ -15,8 +15,6 @@ export interface Vector4Like {
  * 4D vector.
  */
 export class Vector4 {
-    static readonly isVector4: boolean;
-
     constructor(x?: number, y?: number, z?: number, w?: number);
 
     /**
@@ -41,6 +39,7 @@ export class Vector4 {
 
     width: number;
     height: number;
+    readonly isVector4: true;
 
     /**
      * Sets value of this vector.
diff --git a/types/three/test/unit/src/math/Vector3.ts b/types/three/test/unit/src/math/Vector3.ts
new file mode 100644
index 00000000000000..f5d7762faa52ea
--- /dev/null
+++ b/types/three/test/unit/src/math/Vector3.ts
@@ -0,0 +1,4 @@
+import * as THREE from "three";
+
+const texture = new THREE.Vector3();
+texture.isVector3; // $ExpectType true
diff --git a/types/three/tsconfig.json b/types/three/tsconfig.json
index b956c7a63ee8c2..d6421e3a1e85c8 100644
--- a/types/three/tsconfig.json
+++ b/types/three/tsconfig.json
@@ -38,6 +38,7 @@
         "test/unit/src/audio/AudioContext.ts",
         "test/unit/src/core/EventDispatcher.ts",
         "test/unit/src/core/Uniform.ts",
+        "test/unit/src/math/Vector3.ts",
         "test/unit/src/nodes/display/ColorAdjustment.ts",
         "test/unit/src/nodes/materialx/lib/mx_hsv.ts",
         "test/unit/src/nodes/materialx/lib/mx_noise.ts",