diff --git a/pybrake/notifier.py b/pybrake/notifier.py
index 9218c51..c673108 100644
--- a/pybrake/notifier.py
+++ b/pybrake/notifier.py
@@ -295,7 +295,7 @@ class Notifier:
             needed = "/site-packages/"
             ind = s.find(needed)
             if ind > -1:
-                s = "[SITE_PACKAGES]/" + s[ind + len(needed) :]
+                s = "/SITE_PACKAGES/" + s[ind + len(needed) :]
                 return s
 
         s = s.replace(self._context["rootDirectory"], "/PROJECT_ROOT")

diff --git a/pybrake/test_notifier.py b/pybrake/test_notifier.py
index e7bc2d9..8774ef8 100644
--- a/pybrake/test_notifier.py
+++ b/pybrake/test_notifier.py
@@ -205,3 +205,9 @@ def _test_rate_limited():
 
     notice = future.result()
     assert notice["error"] == "IP is rate limited"
+
+def test_clean_filename():
+    notifier = Notifier()
+
+    filename = notifier._clean_filename("home/lib/python3.6/site-packages/python.py")
+    assert filename == "/SITE_PACKAGES/python.py"

[SITE_PACKAGES] -> /SITE_PACKAGES
https://github.com/airbrake/pybrake/blob/master/pybrake/notifier.py#L298
pybrake/test_notifier.py::test_clean_filename
pybrake/test_notifier.py::test_build_notice_from_exception pybrake/test_notifier.py::test_build_notice_from_str pybrake/test_notifier.py::test_build_notice_from_none pybrake/test_notifier.py::test_environment pybrake/test_notifier.py::test_root_directory pybrake/test_notifier.py::test_filter_data pybrake/test_notifier.py::test_filter_ignore pybrake/test_notifier.py::test_filter_ignore_async pybrake/test_notifier.py::test_unknown_host pybrake/test_notifier.py::test_truncation pybrake/test_notifier.py::test_revision_override pybrake/test_notifier.py::test_revision_from_git pybrake/test_notifier.py::test_keys_blacklist_exact pybrake/test_notifier.py::test_keys_blacklist_regexp