diff --git a/js/src/tests/manifest.py b/js/src/tests/manifest.py
index 03add5244bb..0603e208200 100644
--- a/js/src/tests/manifest.py
+++ b/js/src/tests/manifest.py
@@ -7,6 +7,14 @@ from subprocess import *
 
 from tests import TestCase
 
+
+def split_path_into_dirs(path):
+    dirs = []
+    while path != "/":
+        path = os.path.dirname(path)
+        dirs.append(path)
+    return dirs
+
 class XULInfo:
     def __init__(self, abi, os, isdebug):
         self.abi = abi
@@ -29,17 +37,19 @@ class XULInfo:
 
         # Our strategy is to find the autoconf.mk generated for the build and
         # read the values from there.
-        
+
         # Find config/autoconf.mk.
-        dir = jsdir
-        while True:
-            path = os.path.join(dir, 'config/autoconf.mk')
-            if os.path.isfile(path):
-                break
-            if os.path.dirname(dir) == dir:
-                print "Can't find config/autoconf.mk on a directory containing the JS shell (searched from %s)"%jsdir
-                sys.exit(1)
-            dir = os.path.dirname(dir)
+        dirs = split_path_into_dirs(os.getcwd()) + split_path_into_dirs(jsdir)
+
+        path = None
+        for dir in dirs:
+          path = os.path.join(dir, 'config/autoconf.mk')
+          if os.path.isfile(path):
+              break
+
+        if path == None:
+            print "Can't find config/autoconf.mk on a directory containing the JS shell (searched from %s)"%jsdir
+            sys.exit(1)
 
         # Read the values.
         val_re = re.compile(r'(TARGET_XPCOM_ABI|OS_TARGET|MOZ_DEBUG)\s*=\s*(.*)')