Don't attempt to coerce JS strings to numbers
diff --git a/test/test_utils.py b/test/test_utils.py
index 962fd8d753f..c2d1e4fb17a 100644
--- a/test/test_utils.py
+++ b/test/test_utils.py
@@ -994,6 +994,12 @@ def test_js_to_json_edgecases(self):
         on = js_to_json('{42:4.2e1}')
         self.assertEqual(json.loads(on), {'42': 42.0})
 
+        on = js_to_json('{ "0x40": "0x40" }')
+        self.assertEqual(json.loads(on), {'0x40': '0x40'})
+
+        on = js_to_json('{ "040": "040" }')
+        self.assertEqual(json.loads(on), {'040': '040'})
+
     def test_js_to_json_malformed(self):
         self.assertEqual(js_to_json('42a1'), '42"a1"')
         self.assertEqual(js_to_json('42a-1'), '42"a"-1')
diff --git a/youtube_dl/utils.py b/youtube_dl/utils.py
index 01d9c036214..737e2810e22 100644
--- a/youtube_dl/utils.py
+++ b/youtube_dl/utils.py
@@ -4088,12 +4088,12 @@ def fix_kv(m):
                 '\\\n': '',
                 '\\x': '\\u00',
             }.get(m.group(0), m.group(0)), v[1:-1])
-
-        for regex, base in INTEGER_TABLE:
-            im = re.match(regex, v)
-            if im:
-                i = int(im.group(1), base)
-                return '"%d":' % i if v.endswith(':') else '%d' % i
+        else:
+            for regex, base in INTEGER_TABLE:
+                im = re.match(regex, v)
+                if im:
+                    i = int(im.group(1), base)
+                    return '"%d":' % i if v.endswith(':') else '%d' % i
 
         return '"%s"' % v
 

### Before submitting a *pull request* make sure you have:
- [x] At least skimmed through [adding new extractor tutorial](https://github.com/ytdl-org/youtube-dl#adding-support-for-a-new-site) and [youtube-dl coding conventions](https://github.com/ytdl-org/youtube-dl#youtube-dl-coding-conventions) sections
- [x] [Searched](https://github.com/ytdl-org/youtube-dl/search?q=is%3Apr&type=Issues) the bugtracker for similar pull requests
- [x] Checked the code with [flake8](https://pypi.python.org/pypi/flake8)

### In order to be accepted and merged into youtube-dl each piece of code must be in public domain or released under [Unlicense](http://unlicense.org/). Check one of the following options:
- [x] I am the original author of this code and I am willing to release it under [Unlicense](http://unlicense.org/)
- [ ] I am not the original author of this code but it is in public domain or released under [Unlicense](http://unlicense.org/) (provide reliable evidence)

### What is the purpose of your *pull request*?
- [x] Bug fix
- [ ] Improvement
- [ ] New extractor
- [ ] New feature

---

### Description of your *pull request* and other information

The current logic in `js_to_json` tries to rewrite octal/hex numbers to decimal. However, when the logic actually happens the `"` or `'` have already been trimmed off. This causes what were originally strings, that happen to look like octal/hex numbers, to get rewritten to decimal and returned as a number rather than a string.

In practive something like:

```js
{
  "0x40": "foo",
  "040": "bar",
}
```

would get rewritten as:

```json
{
  64: "foo",
  32: "bar
}
```

This is problematic since this isn't valid JSON as you cannot have non-string keys.