diff --git a/resources/idlharness.js b/resources/idlharness.js
index 76131e7c9602b94..d1449cc6c3b6b40 100644
--- a/resources/idlharness.js
+++ b/resources/idlharness.js
@@ -678,6 +678,8 @@ IdlArray.prototype.is_json_type = function(type)
        case "Uint16Array":
        case "Uint32Array":
        case "Uint8ClampedArray":
+       case "BigInt64Array":
+       case "BigUint64Array":
        case "Float32Array":
        case "Float64Array":
        case "ArrayBuffer":
diff --git a/resources/test/tests/unit/IdlArray/is_json_type.html b/resources/test/tests/unit/IdlArray/is_json_type.html
index ab068b29cac0d70..848b90f22994ce8 100644
--- a/resources/test/tests/unit/IdlArray/is_json_type.html
+++ b/resources/test/tests/unit/IdlArray/is_json_type.html
@@ -37,7 +37,10 @@
         assert_false(idl.is_json_type(typeFrom("Uint16Array")));
         assert_false(idl.is_json_type(typeFrom("Uint32Array")));
         assert_false(idl.is_json_type(typeFrom("Uint8ClampedArray")));
+        assert_false(idl.is_json_type(typeFrom("BigInt64Array")));
+        assert_false(idl.is_json_type(typeFrom("BigUint64Array")));
         assert_false(idl.is_json_type(typeFrom("Float32Array")));
+        assert_false(idl.is_json_type(typeFrom("Float64Array")));
         assert_false(idl.is_json_type(typeFrom("ArrayBuffer")));
         assert_false(idl.is_json_type(typeFrom("DataView")));
     }, 'should return false for all buffer source types');