diff --git a/pytest_freezegun.py b/pytest_freezegun.py
index 8bd8573..d5d884b 100644
--- a/pytest_freezegun.py
+++ b/pytest_freezegun.py
@@ -43,5 +43,11 @@ def pytest_runtest_teardown(self):
             self.freezer = None
             self.frozen_time = None
 
+    # pylint: disable=no-self-use
+    def pytest_load_initial_conftests(self, early_config):
+        early_config.addinivalue_line(
+            "markers", "freeze_time: Freeze time using freezegun.",
+        )
+
 
 plugin = FreezegunPlugin()
diff --git a/tox.ini b/tox.ini
index a6c43e8..b8e1a78 100644
--- a/tox.ini
+++ b/tox.ini
@@ -5,6 +5,7 @@ envlist = {py27,py34,py35,py36,pypy}-{pt3,pt4},flake8
 [testenv]
 deps =
   coverage
+  pip >= 19
   pt3: pytest>=3,<4
   pt4: pytest>=4,<5
 commands = coverage run -p -m pytest tests/ {posargs}