--- a/toolkit/components/extensions/Schemas.jsm
+++ b/toolkit/components/extensions/Schemas.jsm
@@ -245,21 +245,18 @@ function parsePattern(pattern) {
 
 function getValueBaseType(value) {
   let type = typeof value;
   switch (type) {
     case "object":
       if (value === null) {
         return "null";
       }
-      switch (ChromeUtils.getClassName(value, true)) {
-        case "Array":
-          return "array";
-        case "ArrayBuffer":
-          return "binary";
+      if (Array.isArray(value)) {
+        return "array";
       }
       break;
 
     case "number":
       if (value % 1 === 0) {
         return "integer";
       }
   }