diff --git a/js/src/tests/ecma_3/Exceptions/15.11.5.js b/js/src/tests/ecma_3/Exceptions/15.11.5.js
index 06902708a85..f61d74ecdc5 100644
--- a/js/src/tests/ecma_3/Exceptions/15.11.5.js
+++ b/js/src/tests/ecma_3/Exceptions/15.11.5.js
@@ -21,15 +21,16 @@ function test()
   enterFunc ('test');
   printStatus (summary);
 
-  var actual = '';
-  var expect = 'TypeError: Error.prototype is not a constructor';
+  var actual = { name: "no error", message: "no message" };
   try {
       new Error.prototype;
   } catch (e) {
-      actual = '' + e;
+      actual = e;
   }
 
-  reportCompare(actual, expect, "not a constructor");
+  reportCompare("TypeError", actual.name, "must be a TypeError");
+  reportCompare(true, /not a constructor/.test(actual.message),
+                "message must indicate not a constructor");
 
   exitFunc ('test');
 }
diff --git a/js/src/tests/js1_5/extensions/regress-429739.js b/js/src/tests/js1_5/extensions/regress-429739.js
index 8d8a20ccec1..fd38b9efe6c 100644
--- a/js/src/tests/js1_5/extensions/regress-429739.js
+++ b/js/src/tests/js1_5/extensions/regress-429739.js
@@ -6,8 +6,6 @@
 //-----------------------------------------------------------------------------
 var BUGNUMBER = 429739;
 var summary = 'Do not assert: OBJ_GET_CLASS(cx, obj)->flags & JSCLASS_HAS_PRIVATE';
-var actual = '';
-var expect = '';
 
 //-----------------------------------------------------------------------------
 test();
@@ -18,20 +16,21 @@ function test()
   enterFunc ('test');
   printBugNumber(BUGNUMBER);
   printStatus (summary);
- 
-  expect = 'TypeError: o.y is not a constructor';
 
+  var actual;
   try
   {
     var o = { __noSuchMethod__: Function }; 
     actual = (new o.y) + '';
+    throw new Error("didn't throw, produced a value");
   }
   catch(ex)
   {
-    actual = ex + '';
+    actual = ex;
   }
 
-  reportCompare(expect, actual, summary);
+  reportCompare("TypeError", actual.name, "bad error name");
+  reportCompare(true, /is not a constructor/.test(actual), summary);
 
   exitFunc ('test');
 }