diff --git a/src/lib/workers/magick.ts b/src/lib/workers/magick.ts
index a2221ea..aa3ab5d 100644
--- a/src/lib/workers/magick.ts
+++ b/src/lib/workers/magick.ts
@@ -293,6 +293,21 @@ const magickConvert = async (
 	let fmt = to.slice(1).toUpperCase();
 	if (fmt === "JFIF") fmt = "JPEG";
 
+	// ICO size clamp to avoid WidthOrHeightExceedsLimit
+	if (fmt === "ICO") {
+		const max = 256;
+		const w = img.width;
+		const h = img.height;
+
+		if (w > max || h > max) {
+			const scale = max / Math.max(w, h);
+			const newW = Math.max(1, Math.round(w * scale));
+			const newH = Math.max(1, Math.round(h * scale));
+
+			img.resize(newW, newH);
+		}
+	}
+
 	const result = await new Promise<Uint8Array>((resolve, reject) => {
 		try {
 			// magick-wasm automatically clamps (https://github.com/dlemstra/magick-wasm/blob/76fc6f2b0c0497d2ddc251bbf6174b4dc92ac3ea/src/magick-image.ts#L2480)