diff --git a/global.go b/global.go
index 995ec35..8d6b0b8 100644
--- a/global.go
+++ b/global.go
@@ -704,8 +704,8 @@ func newContext() *_runtime {
 		"eval", -1, builtinGlobal_eval,
 		"parseInt", -2, builtinGlobal_parseInt,
 		"parseFloat", -1, builtinGlobal_parseFloat,
-		"isNaN", builtinGlobal_isNaN,
-		"isFinite", builtinGlobal_isFinite,
+		"isNaN", -1, builtinGlobal_isNaN,
+		"isFinite", -1, builtinGlobal_isFinite,
 		"decodeURI", builtinGlobal_decodeURI_decodeURIComponent,
 		"decodeURIComponent", builtinGlobal_decodeURI_decodeURIComponent,
 		"encodeURI", builtinGlobal_encodeURI,
diff --git a/global_test.go b/global_test.go
index b01c251..a97c8eb 100644
--- a/global_test.go
+++ b/global_test.go
@@ -93,6 +93,9 @@ func Test_isNaN(t *testing.T) {
 	test(`isNaN()`, "true")
 	test(`isNaN(NaN)`, "true")
 	test(`isNaN(Infinity)`, "false")
+
+	test(`isNaN.length === 1`, "true")
+	test(`isNaN.prototype === undefined`, "true")
 }
 
 func Test_isFinite(t *testing.T) {
@@ -105,6 +108,9 @@ func Test_isFinite(t *testing.T) {
 	test(`isFinite(NaN)`, "false")
 	test(`isFinite(Infinity)`, "false")
 	test(`isFinite(new Number(451));`, "true")
+
+	test(`isFinite.length === 1`, "true")
+	test(`isFinite.prototype === undefined`, "true")
 }
 
 func Test_parseInt(t *testing.T) {