diff --git a/js/src/devtools/automation/autospider.py b/js/src/devtools/automation/autospider.py
index 03081738d2e4..a50e368f62d5 100755
--- a/js/src/devtools/automation/autospider.py
+++ b/js/src/devtools/automation/autospider.py
@@ -32,6 +32,7 @@ def directories(pathmodule, cwd, fixup=lambda s: s):
 DIR = directories(os.path, os.getcwd())
 PDIR = directories(posixpath, os.environ["PWD"],
                    fixup=lambda s: re.sub(r'^(\w):', r'/\1', s))
+env['CPP_UNIT_TESTS_DIR_JS_SRC'] = DIR.js_src
 
 parser = argparse.ArgumentParser(
     description='Run a spidermonkey shell build job')
diff --git a/testing/runcppunittests.py b/testing/runcppunittests.py
index d9e4f01c4a58..573da30d24a5 100755
--- a/testing/runcppunittests.py
+++ b/testing/runcppunittests.py
@@ -8,6 +8,7 @@ from __future__ import with_statement
 import sys
 import os
 from optparse import OptionParser
+from os import environ as env
 import manifestparser
 import mozprocess
 import mozinfo
@@ -17,6 +18,9 @@ import mozlog
 
 SCRIPT_DIR = os.path.abspath(os.path.realpath(os.path.dirname(__file__)))
 
+# Export directory js/src for tests that need it.
+env['CPP_UNIT_TESTS_DIR_JS_SRC'] = os.path.abspath(os.path.join(SCRIPT_DIR, "..", ".."))
+
 
 class CPPUnitTests(object):
     # Time (seconds) to wait for test process to complete