diff --git a/js/src/tests/js1_8_5/regress/regress-559438.js b/js/src/tests/js1_8_5/regress/regress-559438.js
index 53a98d7a3aa8..c2b440c181bb 100644
--- a/js/src/tests/js1_8_5/regress/regress-559438.js
+++ b/js/src/tests/js1_8_5/regress/regress-559438.js
@@ -6,5 +6,5 @@
 
 function f(x) { return 1 + "" + (x + 1); }
 reportCompare("12", f(1), "");
-var g = eval(String(f));
-reportCompare("12", f(1), "");
+var g = eval("(" + f + ")");
+reportCompare("12", g(1), "");