diff --git a/lib/utils/fun.js b/lib/utils/fun.js
index 75e314d..884ed11 100644
--- a/lib/utils/fun.js
+++ b/lib/utils/fun.js
@@ -6,7 +6,7 @@ const isDefined = (v) => v && (typeof v) != "undefined";
 const isBoolean = (v) => (typeof v) === "boolean";
 const isInteger = (v) => Number.isInteger(v);
 const isDate = (v) => (v instanceof Date);
-const isBinary = (v) => (v instanceof ArrayBuffer);
+const isBinary = (v) => (v instanceof Uint32Array);
 
 const isStringOrThrow = (v, t) =>
   (isString(v)