diff --git a/tests/test_helpers.py b/tests/test_helpers.py
index 6dc41fad..2338844e 100644
--- a/tests/test_helpers.py
+++ b/tests/test_helpers.py
@@ -19,6 +19,10 @@ from werkzeug.exceptions import BadRequest
 from werkzeug.http import parse_cache_control_header, parse_options_header
 from werkzeug.http import http_date
 from flask._compat import StringIO, text_type
+try:
+    import simplejson
+except ImportError:
+    import json as simplejson
 
 
 def has_encoding(name):
@@ -114,6 +118,10 @@ class TestJSON(object):
             assert rv.mimetype == 'application/json'
             assert flask.json.loads(rv.data) == d
 
+    def test_simplejson_does_not_escape_slashes(self):
+        """Test that \\/ is no longer standard behavior."""
+        assert '\\/' not in simplejson.dumps('/')
+
     def test_jsonify_dicts(self):
         """Test jsonify with dicts and kwargs unpacking."""
         d = dict(
diff --git a/tox.ini b/tox.ini
index bd936a4b..5e879cec 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,5 +1,5 @@
 [tox]
-envlist = {py26,py27,pypy}-{lowest,release,devel}, {py33,py34,py35}-{release,devel}
+envlist = {py26,py27,pypy}-{lowest,release,devel,simplejson}, {py33,py34,py35}-{release,devel,simplejson}
 
 [testenv]
 commands =
@@ -19,6 +19,7 @@ deps=
     devel: git+https://github.com/pallets/jinja.git
     devel: git+https://github.com/pallets/itsdangerous.git
     devel: git+https://github.com/jek/blinker.git
+    simplejson: simplejson
 
 [testenv:docs]
 deps = sphinx