diff --git a/src/types.ts b/src/types.ts
index 87cb587..8769bad 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -1,8 +1,19 @@
+/**
+ * A type wider than `number[]`, omitting any instance functions
+ * unused by the API, e.g., map, sort. This allows the math
+ * functions to operate on a wider range of array-like
+ * values.
+ */
+export interface MutableNumberArray {
+	readonly length: number;
+	[n: number]: number;
+}
+
 /**
  * The types you can pass to most functions that take an
  * array of numbers.
  */
-export type BaseArgType = Float32Array | Float64Array | number[];
+export type BaseArgType = Float32Array | Float64Array | MutableNumberArray;
 
 function wrapConstructor<T extends new(...args: any[]) => any>(
   OriginalConstructor: T,
diff --git a/src/wgpu-matrix.ts b/src/wgpu-matrix.ts
index d757056..4f51b2f 100644
--- a/src/wgpu-matrix.ts
+++ b/src/wgpu-matrix.ts
@@ -2,7 +2,7 @@
  * Some docs
  * @namespace wgpu-matrix
  */
-import {BaseArgType, ZeroArray} from './types';
+import {MutableNumberArray, BaseArgType, ZeroArray} from './types';
 import {Mat3Arg, Mat3Type, getAPI as getMat3API} from './mat3-impl';
 import {Mat4Arg, Mat4Type, getAPI as getMat4API} from './mat4-impl';
 import {QuatArg, QuatType, getAPI as getQuatAPI, RotationOrder} from './quat-impl';
@@ -15,6 +15,7 @@ export {
   RotationOrder,
   utils,
 
+  MutableNumberArray,
   BaseArgType,
 
   Mat3Arg,