diff --git a/src/add-sample.ts b/src/add-sample.ts
index 4326a80..b078203 100644
--- a/src/add-sample.ts
+++ b/src/add-sample.ts
@@ -1,4 +1,4 @@
-import { loadImage, srgbToOklab } from './utils'
+import { isImageElement, loadImage, srgbToOklab } from './utils'
 import type { Context } from './context'
 
 interface AddSampleOptions {
@@ -35,7 +35,7 @@ export function addSample(
         options,
       )
     })
-  } else if (source instanceof HTMLImageElement) {
+  } else if (isImageElement(source)) {
     if (!context2d) return
     context2d.canvas.width = source.width
     context2d.canvas.height = source.height
diff --git a/src/create-palette.ts b/src/create-palette.ts
index eef7efa..8278357 100644
--- a/src/create-palette.ts
+++ b/src/create-palette.ts
@@ -10,7 +10,7 @@ import type { Context } from './context'
 import type { Palette } from './palette'
 import type { Options } from './options'
 
-export function createPalette(options: Options | Context): Palette {
+export function createPalette(options?: Options | Context): Palette {
   const context = orCreateContext(options)
 
   const {
diff --git a/src/utils.ts b/src/utils.ts
index ee75797..ee79f84 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -1,6 +1,7 @@
 import type { ColorSample, Oklab, Sort } from './types'
 
 export const IN_BROWSER = typeof window !== 'undefined'
+export const isImageElement = (node: any): node is HTMLImageElement => node && typeof node === 'object' && node.nodeType === 1 && node.tagName === 'IMG'
 
 const K = (1 << 16) - 1
 const K2 = K * K